Here's a fun fact that almost isn’t part of this story.

One of my wife's friends has a kidney disorder that is being studied and closely monitored by doctors at the University in Madison. She isn't supposed to drive, so my wife volunteered to be her taxi. They leave after dinner on Thursday evenings and then spend the night. My wife is usually home by noon on Friday. This has been going on for months, and they plan to continue for the foreseeable future.

===

As the next Thursday rolled around, the temptation to call my sister-in-law and arrange something was strong. I had two problems with that. First, I didn't want to let my sister-in-law know how eager I was to have her come back for more pictures. And second, although it probably should have been first, we knew that she was having marital problems. She needed support with that more than she needed to be seduced by me.

It was certainly enough that she knew where to find me and she also had to have been aware of the opportunity. I made sure that the camera batteries were charged and the sheets were clean, and I waited. I was almost ready to give up when a car pulled into the driveway. I was shocked as hell when my other sister-in-law, Kathy, came storming into the house.

Apparently, she was angry. She didn't say hello or anything.

"You miserable son-of-a-bitch!" she spat at me.

I quickly chose honey over fists.

"Kathy, darling, my favorite sister-in-law, how pleasant of you to stop by. To what do I owe this honor?"

She glared at me because she knew what I was trying to do.

"How many times have you spurned me for trying to seduce you? I know she's cute 'cause she's the baby, but why would you just fuck her when you’ve ignored me when I've been trying all these years?"

I tried to deflect her later questions by attacking the first one.

"It was once, and we both know it would have gotten us into trouble."

She glared harder.

"Don't pretend like it hasn't been at least four times."

"Four?" I couldn't believe it had been that many.

"The first time was when you took the pictures," she suggested.

"What?" I'm sure she saw how shocked I was.

"I was a virgin, and Becky promised she would let you seduce me. We both thought you would make my first time special."

"Neither of you said anything," I protested.

"Go look at the pictures again," she insisted. "Even Tom noticed how my eyes were begging you to fuck me! He couldn't believe that you didn't do it."

"I don't know what to say," I offered. "I hadn't been married twenty-four hours and I was paying more attention to getting rid of you so I could fuck my wife."

Her eyes flared, but I couldn't tell if it was anger or acknowledgment of my lust.

"What about California?" she demanded

For a short period of time, Kathy had wanted to prove that she could survive on her own. She had nearly run away to go live near Los Angeles and work at one of the big theme parks there. When she decided she was going to stay, she convinced my wife and me to drive out to visit and deliver some of her things.

Before we got there, Kathy had had a big fight with the boyfriend she had met out there. The night after we got there, we had hired a babysitter for our kids so Kathy could take us out to see the sights. We had run into her boyfriend, they had fought again, and Kathy proceeded to get excessively drunk. We managed to get her home, and because my wife can't stand the smell of vomit, I ended up holding Kathy all night and cleaning up every time she puked.

The next night, my wife conveniently went to bed early with the kids, and Kathy curled up next to me on the couch to thank me for being good to her the night before. She had made it very clear that her thanks would allow me to take anything I wanted. I thought I had been very clear when I had explained that all I was taking was a cuddle and a kiss.

"I told you back then, and it was true," I reminded her. "Becky may have said it was alright, but she was feeling very self-conscious about the weight she had put on during her pregnancy. If I had slept with you, it would have killed her inside."

She gave me a skeptical look, which quickly changed to a challenging smile.

"And Theresa's bachelorette party?"

"Seriously?"

I had been conned into being the designated driver for seven drunk and boisterous women. After dancing up a storm, Kathy had dragged me out of the bar to get some fresh air. The kiss she had given me left little doubt about the other things she wanted.

Her eyes continued to challenge me to answer.

"No matter how wild you think your sister and I may be, there was no chance that I was going to have sex with you on that patio. There were security cameras everywhere. You saw how much trouble we got in when your sisters and their friends caught us kissing!"

"Yeah? What about the cabin at Christmas?"

I didn't have to fake the surprised look I gave her. I had no idea what she was talking about.

"I have no idea..." I started to say.

She blushed and gasped loudly, and then her eyes dropped nervously to the floor.

"I think I know why Tom's brother has been giving me odd looks, then," she said in a worried tone. Her brows furrowed, and her eyes were almost angry again when they swept back up to glare at me.

"It doesn't matter," she insisted. "Here's what's going to happen. I'm going to go upstairs and pick out some things to model. You're going to get your camera and take some new pictures for my husband.

"I'm going to make sure you're nice and hard. If you convince me that you're properly apologetic about the past, I will take care of you. Otherwise, I'm going to make sure you suffer blue-balls tonight!"

Without waiting for my opinion, she turned and stormed upstairs.

I have to revise my list. There are four reasons that I was headed for trouble. First was the sisters' egos. Second, was the batch of old photos. Third, was how I spoil my wife. Fourth is my wife's family's libido.

I don't have direct experience with her two older sisters, but I've heard stories. In addition to my recent experiences with her younger sisters, I've heard stories about them as well. It was my wife's idea that she and I start swinging, and she is usually one of the first to get naked at parties. Along with my wife, the sisters are all sexual dynamos who can never get enough.

Tragically, I think the problem is worse with their daughters. Several of the nieces are in their twenties, just like my daughter. Some of the stories I've heard about them just about make me blush. It’s enough to cause fits for a father and uncle.

As I grabbed my camera and headed upstairs, I had no doubt that her threat was empty. I would have been surprised if we made it through a dozen poses before we started having sex.

I had to stop at the bedroom door and gawk. She was standing naked in front of the mirror, holding two outfits. She is taller than her younger sister and my wife, and she has almost no body fat. In spite of that, she has great curves in all the right places. She turned to me with a smile and then held first a sapphire lace panty and bra set and then an emerald green teddy in front of her body.

"I can't decide which one," she teased, offering the choice to me.

"We'll have to do both," I suggested with a laugh.

"Really?" she gasped. Her eyes appraised me in a way that made me think she was reading more into my statement than I had meant. I didn't have any problems with that at all.

"If you have time," I allowed.

"We'll have time!" she cried. Her eyes narrowed. "You need to be naked so I can be sure I've made you hard."

I gave her a wry smile and a laugh. I quickly removed my clothes and she quickly put on the bra and panties. I took a moment to really look at her, and I saw that she had already put on a bit of makeup. She was just as pretty as her sisters, and she didn't need much. She had just enough to work with the flash. She ignored my scrutiny as she walked over and grabbed my cock. It wasn't fully hard, but it was stiff enough.

"I want you harder than that if I'm going to punish you," she quipped. "What pose do you want first?"

She moved to the bed and I started snapping away.

While my wife and her youngest sister tend to keep their hair short, Kathy's dark streaked blond hair was very full and reached to the middle of her back. We did several poses with her lying back with her hair spread on the bed. My favorite was a side view shot with her arms tucked under her arched back and her face only partially turned to the camera.

Each time she changed her pose, she lustfully reached out and stroked my cock. It was fully hard, but she still pretended she needed to check it. The third time she reached for me, I managed to capture her lustful look on film. She glared at me for taking the picture, and then she reached out and pulled me close for a very demanding kiss. It was very hard to keep taking pictures after that.

The lacy bra had a front release. She opened it and we took photos in several poses with her breasts partially and fully exposed. When she went to stroke my cock on a pose change, I caught her breast and teased her nipple. Her nipples don't get as hard as her younger sister's, but they were still delightful to play with. On the next change, she pulled my face down to suck on her breast, and we both enjoyed that.

The kissing, teasing, and stroking continued as she removed the bra for several poses. We took more photos with her on her back and her side, and then she rolled into the classic ass-up-shoulders-down pose. We took several styles of shots that way, but when she moved to change, I stopped her.

"Hold on, we have one more to do this way," I suggested.

"It better be with the panties rolled half-way off," she demanded. "I need them off so I can take you inside to truly feel if you are hard enough for me to punish."

"Trust me, this is pure torture already," I replied. "Pull your panties aside and spread your lips with your fingers."

She complied and I took several pictures.

"Oh, that's no good," I complained as I quietly set the camera down.

"What's wrong?" she begged, sounding worried.

"The shiny areas are reacting with the flash," I explained. "Let me see if I can remove some of that moisture."

She shrieked in surprise when I grabbed her hips from behind and smashed my face between her legs. She tried to drop and kick away, but I had a firm hold on her. I forced my tongue deep inside her and then swirled my way down to her clit. She continued to kick and thrash as an orgasm exploded through her body. I kept my face buried deep in her ass cheeks, even though she nearly drowned me.

As lost as I was in lust, I still had time to be surprised by the differences between the sisters. My wife has dryness issues, and we have to be careful to keep her lubricated during sex. Both of her younger sisters were fountains of wetness. My wife has a strong, sweet flavor that I love. The youngest sister has an even stronger musky flavor. It will never happen, but I would love to taste the two of their flavors mixed. Kathy's flavors were sweet, but very faint.

Even before her orgasm ended, she kicked free by knocking me on my side. She turned and pounced, pinning my shoulders to the bed.

"You son-of-a-bitch," she cried out. She even sounded angry. Her words and actions betrayed her. "You don't get to just make me cum whenever you want! I'm the one doing the fucking, not you!"

She managed to thrust backwards, pull the panties aside, and impaled herself in one smooth motion. She cried out and growled at the same time, and then she started slamming her hips against me. Her lips slammed into mine as she eagerly tasted her own flavors on my lips. I tried to grab her hips, to slam up into her, but she wrestled my arms over my head and held them there as she controlled our speed and depth. She didn't last very long.

"Son-of-a-bitch!" she cried out. "You're fucking making me cum!" I started to protest, but her eyes bored into mine and she cried out, "Fill me! Fill me now!"

She exploded into another orgasm, and I gave in to her demands. She collapsed into a quivering mass on top of me. I couldn't stop myself from sliding my hands down to squeeze her ass while I pushed my surging cock into her as deeply as I could. She cried and trembled and kissed me as we melted into each other's arms.

We lay together for quite a while. Neither of us said anything, and I caressed her ass and lower back. After a long while, she took a deep breath, and then pushed up off of my chest. I'll be damned if she didn't have the same fire in her eyes that her sisters have.

"Are you ready to move on to the green one?" she asked nicely.

I took a deep breath and sighed with a smile on my face.

"I could probably use another minute," I suggested. "Let me check the camera battery."

Her smile turned naughty and she rolled her hips and ass against me. My flaccid cock popped out of her, followed by a gush of heat. We both trembled with pleasure.

"I think you're lying," she accused. "I think I'm going to have to punish you again."

"I'm lying?" I asked.

"You're supposed to be hard while I make love to the camera," she insisted. "I'm going to have to make you hard again to torture you."

In a flash, she slid down my body and sucked my cock into her mouth. I was way too sensitive, and trying to pull away only increased the friction that she was using to torture me. Even worse, my cock grew even more sensitive as it quickly grew in her mouth. She moaned in delight as she worked me up to full hardness.

"Now you're ready," she cooed as she sprang off the bed.

She quickly peeled the wet panties off and pulled the emerald green teddy on. I grabbed the camera and took several quick pictures. She rolled onto her back on the bed and beckoned for me to move close.

"You better do as your told this time," she insisted with her naughty smile beaming. "Put your cock inside me so I can tell if you're hard enough to torture."

I managed to crawl between her legs and lift her hips enough to press inside her. At the same time, I took several pictures. I nicely caught the look on her face when her eyes rolled back to enjoy the feeling of my cock sliding inside.

"Fuck me slowly while I tease the camera," she moaned. Her eyes were closed, but I could feel her body responding to the sound of the camera. Without ever opening her eyes, she seemed to know exactly how to pose for the camera.

As I slowly stroked in and out of her, I started to adjust my hips to search for her g-spot. She barely noticed until my cock found the spot, and she gasped as her eyes flew open. The camera perfectly captured the raw sexual astonishment on her face.

After I made her jump with several strokes across her most sensitive spot, her eyes managed to focus on my face.

"You're doing that on purpose!" she accused.

I smiled, and snapped more pictures.

"I feel this with Tom sometimes," she gasped. "But never like this! You're going to make me cum!"

"I think I should torture you. I think I should stop," I teased.

I didn't stop. She lost the ability to ask me to, as her eyes rolled back and a slow, intense orgasm claimed her. The camera caught it all. I kept her cumming for several minutes with the slow strokes across her g-spot. I would have kept going, but she was gasping for air and waving her hand for me to stop.

As soon as her eyes opened, I said, "This is what happens when you come into my house and threaten to be mean to me. I've half a mind to torture you some more, and never stop."

Her smile was very willing, but her head shook from side to side.

"I don't think my body could handle another orgasm right now," she suggested.

I'm pretty sure she saw my eyes light up. I didn't give her time to worry about it.

"I don't think you have a choice," I suggested as my body fell forward over hers.

The camera was all but forgotten as I started hammering her with deep, hard thrusts. Her eyes went wide as another orgasm immediately exploded through her, and she cried out when my cock swelled and exploded inside her. We clung together and rode the intense waves of pleasure together.

Just as I was going to collapse, she grabbed my head and pulled it up so she could look deep into my eyes. She almost spoke twice, but she stopped before any words came out. Finally, she swallowed and smiled at me.

"Tell your wife that I love her very...