Robert, sweat beading on his brow, lugged in the final suitcase into the cramped apartment, dropping it with a thud beside the mountain of Tracy's other belongings. Tracy, her hands on her hips and a scowl on her flushed face, let out a sigh that had a mix of anger and despair. "I just can't believe they'd do this to me," she spat out, her voice tight with emotion. "Kick me out like I'm some kind of...some kind of whore."

"Welcome to the club, sis," Rob said with a forced chuckle, wiping his forehead with the back of his hand. "I've been living without their loving embrace for three years now. Trust me, it's not all bad." He glanced around the tiny living room, the walls adorned with peeling paint and the furniture a hodgepodge of hand-me-downs and thrift store finds. "I mean, it's not like they were the poster family for the perfect home life, anyway."

"But the baby, Robby," Tracy whispered, her eyes welling up with tears. "They wanted me to abort it after Tom left me."

"Fuck 'em," Rob responded, his voice firm, a rare show of emotion from the typically reserved man. "You and the baby deserve better than that. Besides," he added with a wink, "now you're with me, and I'm the best big brother you could ask for." He wrapped his arms around her in a comforting hug, feeling the soft swell of her belly pressing against him.

They had always been close, the two of them. The harsh realities of their upbringing had forged an unbreakable bond. Their parents had never been the nurturing type, favoring the iron fist to the gentle hand. Robert had moved out at the ripe age of 23, eager to escape the oppressive atmosphere of their family home. Now, at 26, he had carved out a simple life for himself, working the evening shift at the local warehouse, driving a forklift from 2 to 10pm. It was a job that paid the bills and left him with plenty of time to himself, which was all he ever really wanted.

Tracy, on the other hand, had just turned 19, and was now six months pregnant with a baby she had not planned for. The father, a no-good layabout who had abandoned her the moment he heard the news, was a distant memory she liked to keep buried. Their parents had been furious, demanding she get an abortion and threatening to disown her if she didn't. But Tracy was stubborn, a trait she had inherited from her mother, unfortunately. She had refused, and so here she was, moving into Robert's tiny apartment with nothing but a few suitcases and boxes.

Robert had taken a week's vacation after his sister told him what happened. He invited her to stay with him, and they had spent the week trying to make the place feel more like a home, and less of a bachelor pad. They spent the time unpacking, going out to eat, and watching movies, pushing aside the memories of their past. Now she felt a sense of comfort, a warmth that she hadn't felt in months.

"Thank you," she said to him one evening while watching a movie together. "For everything."

"Anything for you, Trace."

The next day, the routine of life began to reassert itself. The week's vacation was over, and Robert had work later that day. His stomach rumbled as he entered the kitchen, the aroma of Tracy's breakfast wafting through the air. She had insisted on cooking for him, eager to contribute despite her pregnancy. He gave her a quick peck on the forehead before sitting down for breakfast. She really only knew how to make eggs, but she did it well and changed the style and ingredients to keep it different. They spent the morning watching more movies and TV shows, before he left for work.

It was as if his hiatus from work never happened, getting right into the swing of emptying and organizing pallets of goods, the warehouse's fans buzzing above him like a hive of giant, mechanical bees. The monotony of his shift gave him plenty of time to think of his sister and how he enjoyed having her live with him.

But when he returned home, the mundane was shattered like a dropped beer bottle in a quiet alley. Tracy was standing in the kitchen, her plump breasts bared to the cold embrace of the open fridge, the light casting a heavenly glow upon her naked torso. He had no idea for what reason she was doing this, but the sight of her topless form was like a bolt of lightning to Robert's groin. He had not had sex in over a year, and the sight of her nakedness sent a jolt of pure, raw desire through him. He had to clench his fists to stop himself from reaching out to touch her.

"Tracy!" he exclaimed, his voice a mix of shock and arousal.

"Oh, shit, Robby," she squealed, spinning around to face him, her cheeks a brilliant shade of scarlet, trying to cover her breasts with her arms, which at their size, wasn't possible, but she at least covered her nipples. "I'm so sorry, I didn't know you were home. I had a massive hot flash and this was the only thing I could think to do."

"Oh," he managed, his eyes glued to her breasts. "I just didn't expect..."

"Yeah, sorry about that," she mumbled, hastily grabbing her tank top and pulling it over her head. "I've been getting these hot flashes. It's probably just the pregnancy."

"Maybe you should see a doctor," he suggested, his voice thick with lust he couldn't hide. "Make sure everything's okay."

"I've got it under control," she said with a dismissive wave. "It's just hormones playing tricks on me."

But the image of his sister, her skin flushed and her nipples hardened with the cold, was burned into his brain. That night, he lay in bed, unable to sleep, a wholly unwelcome erection keeping him awake.

The next day, when he returned from work, he found Tracy sprawled out on the couch, her shirt hiked up and her breasts exposed. She was sound asleep, her chest rising and falling with each breath. He felt his cock throb at the sight, and his heart pounded in his chest. He found himself unable to move, just staring at how perfect her breasts looked as she lay back, her nipples proudly standing erect. Breaking out of his spell, he quietly walked to the foot of the couch and shook her foot by her big toe. She stirred, slowly waking up.

"Robby?" she murmured, a smile playing on her lips.

Robert said nothing, just up-nodded towards her torso. She looked down and gasped, pulling her shirt down in a rush. "I'm sorry," she said softly, blushing.

He nodded, his cheeks burning. "It's okay," he said, his voice catching in his throat.

The next morning, Tracy was in the kitchen, her rounded belly pressing against the counter as she whipped up a breakfast of eggs and toast. Robert sat at the table, his eyes flicking up to her every so often, watching as she moved with a grace that seemed almost impossible with the weight she carried. She looked up at him and smiled, her cheeks dimpling, and his heart skipped a beat.

Suddenly, she gasped, her hand shooting to the bottom of her tank top, fanning herself with it. "Hot flash," she murmured, her eyes squeezed shut as she tried to cool down.

"Want me to turn on the AC?" he offered, his eyes never leaving her face.

"No, it's fine," she said through gritted teeth, but she kept fanning herself, inching the shirt higher and higher until the underside of her breasts were peeking out.

Each time she brought the shirt up, it was a tease, a tantalizing glimpse of the flesh he had grown so fond of. And then she couldn't take it anymore. With a sound of frustration, she pulled the shirt off over her head, standing in front of him in just her old sweatpants, her bare breasts exposed. The kitchen was like a sauna, the heat from the stove mixing with her own internal fire.

Rob's eyes widened, his throat going dry as he took in the sight of her. Her breasts were swollen with pregnancy, her nipples dark and tight. He swallowed hard, trying to ignore the insistent throb in his pants.

But then she gasped, doubling over, her hand pressing into her lower belly. "Oh God," she panted, her eyes squeezed shut.

Robert shot out of his chair, his heart racing. "Tracy? What's wrong?"

"It's a... contraction," she managed, her face scrunched in pain.

He was at her side in a second, his hand on her back, rubbing soothing circles. "Are you okay?"

"I think so," she gasped, but before she could say more, another contraction hit, this one stronger than the last. She stumbled forward, and Robert caught her, his hand landing on her bare breast by mistake.

Her eyes shot open, wide with shock and embarrassment, and she clung to him as the pain ripped through her. His hand remained on her breast, her softness and warmth a stark contrast to the coldness of the kitchen floor.

When the contraction passed, she took a shaky breath, looking up at him. They both knew what had happened, but neither of them said a word. She quickly pulled her shirt back on, hiding herself from his gaze. "We should... make that appointment," she said, her voice quivering.

"Yeah," he agreed, his voice hoarse. "We should."

He called into work, telling them he had a family emergency. The next phone call was to the local gynecologist, and they needed an appointment that day.

It was a quick drive to the office, and the receptionist was kind, asking for their names and information with a smile on her face.

When they were called back into the exam room, Tracy was instructed to lie down on the table. The nurse told her to lift up her shirt and lower her sweatpants to fully expose her belly.

"Okay," Tracy whispered, her cheeks aflame as she complied.

Robert hovered by her side, his hand hovering in the air, unsure of what to do. He watched as the nurse smeared cold gel on Tracy's bare skin, his sister's breath catching in her throat.

"You okay?" he asked, his voice tentative.

"Yeah," she nodded, her eyes squeezed shut. "Just cold."

The nurse, a stern-looking woman with a no-nonsense attitude, turned to Robert. "You need to be here for support. Hold her hand or put your hand on her shoulder."

He nodded, taking her hand and giving it a gentle squeeze. Tracy's skin was hot to the touch, a stark contrast to the cool gel.

The nurse began to probe her stomach with the ultrasound wand, searching for the baby's heartbeat. Suddenly, another contraction hit Tracy like a truck, her back arching off the table.

"Oh God," she groaned, her eyes flying open.

The nurse looked at her with a frown. "You're having a contraction. It's okay, but you need to relax."

"It's just..." Tracy began, but then another contraction took her, her body tensing up like a bowstring.

Robert could see the pain in her eyes and felt helpless. He wished he could do something, anything, to make it go away.

The nurse leaned in closer, her eyes on the screen. "You know, sometimes an orgasm can help alleviate the pain of contractions."

Both Robert and Tracy stared at her in shock. "What?" they exclaimed in unison.

"It's true," the nurse said, not taking her eyes off the screen. "Orgasms release endorphins, which can help with the pain. It's not uncommon for women to masturbate during early contractions to help manage it."

"But..." Robert began, his cheeks reddening.

"Don't be shy," the nurse said, cutting him off. "You're not here for fun and games. This is for medical reasons. You don't want your wife in pain, do you?"

Tracy looked at him, her eyes pleading. He felt his stomach drop. The nurse thought they were married. They had the same last name, after all. He had never been in a situation like this before, but he knew he had to do something.

The nurse took Robert's hand and placed it inside Tracy's sweatpants. "Just help her out, okay?"

With trembling hands, Robert began to rub Tracy's vulva, feeling her heat and the dampness of her arousal through the fabric. This was his sister, and the act was both terrifying and exhilarating.

Tracy's breath hitched, and she looked at him with a mix of embarrassment and gratitude. "Just... be gentle," she whispered.

He nodded, his thumb finding her clit. He began to massage her, unsure of just what the fuck was going on, but trying to be as gentle as he could.

The nurse nodded in approval, her eyes never leaving the screen. "That's good," she murmured. "Keep going."

Tracy's hips began to move in time with Robert's touch, her breath coming in short gasps. He could see the tension in her body start to ease, the contractions becoming less intense.

"Is it helping?" he asked, his voice low.

"Yeah," she panted, her eyes never leaving his. "Keep going."

He slid his middle finger inside her, sliding through her moisture. His thumb caressed her hardened clit gently, finger penetrating slowly, her body responding to his touch. The intimacy of it was almost too much to handle.

But he pushed through, his love for his sister overriding any awkwardness he felt. He wanted to help her, to make her feel better.

Tracy's legs clamped around Robert's hand like a vise, her thighs trembling as she grabbed his wrist. Her eyes rolled back into her head, and she let out a low moan, her hips moving in a desperate, primal rhythm against his touch. She guided him, urging him on as she rode the waves of pleasure and pain that crashed through her body.

Her breath grew ragged, her breasts heaving with each pant. The nurse looked up from the ultrasound machine, noticing the change in her expression. "That's it," she said, her voice softening. "Just let it happen."

Robert could feel the tension building in Tracy's body, her muscles tightening around his fingers. He didn't know if this was right, but he knew he didn't want to stop. He wanted to make her feel good, to take away the pain.

With a sudden jolt, she came, her entire body convulsing with the force of her orgasm. She cried out, her nails digging into the skin of his wrist. He stared at her in amazement, watching as the contractions subsided, her body going limp against his hand.

The nurse nodded in approval. "Good job," she said, her voice matter-of-fact. "Now, let's get this ultrasound done."

Robert pulled his hand away, his heart racing. He couldn't believe what had just happened. He had just made his sister cum in a doctor's office, and she had liked it.

Tracy lay there, her cheeks flushed and her chest heaving. She looked up at him with a mix of relief and embarrassment, her eyes wide with shock. "Thank you," she murmured.

He nodded, his throat tight. "Yeah," he said, his voice hoarse.

The nurse began the ultrasound, the cold gel on Tracy's belly feeling like ice water against Robert's hot hand. He couldn't stop staring at his sister's breasts, the way they moved with each breath she took.

The room was silent except for the whir of the machine, and the occasional beep that signaled the baby's heartbeat. It was a strange, intimate moment, one that Robert knew would change their relationship forever.

When the nurse was done, she wiped the gel off Tracy's belly and handed her a towel to clean herself up. "Everything looks fine," she said, her voice professional once again. "Just some Braxton Hicks contractions, just stronger than usual. Nothing to worry about."

The drive home was tense, the air thick with unspoken words. Tracy stared out the window, her hand resting protectively on her stomach, and Robert focused on the road, his mind racing with a tornado of thoughts and emotions.

Finally, when they pulled into the parking lot of their apartment complex, he turned to her. "Are you okay?" he asked, his voice tentative.

Tracy nodded, but didn't meet his gaze. "It was just the contractions," she murmured. "They're normal."

Robert nodded, his heart racing. "But what happened in there..."

"It was for medical reasons," she said softly. "Right?"

"Yeah." He nodded, slowly. "For medical reasons. And... if you have more contractions?"

She swallowed, her throat suddenly dry. "We know how to take care of them, now."

Robert nodded. "And I'll help you."

Tracy put her hand over his. "Yeah. You'll always be there for me."