I am Fred and some years ago, at the time of these events, I was 16 years old and my sister Ruth was a year older. Next door was a family which had a swimming pool. The family included a son and daughter that were the same age as Ruth and me. Sometimes we were invited to swim in the pool. On this occasion we swam in the pool without our parents, who were out at work in their various offices.

The brother and sister were Tom and Sue and we were all sitting at the side of the pool after our swim. When we were chatting together Tom said that as our parents weren`t with us we could swim in the nude. To that Ruth said that Fred and she had never been naked together, nor, of course, with Tom and Sue. She asked me if I thought we should swim naked and my reply was that it would be fun so we should do it. 

With great daring (as far as my sister and I were concerned) we all took off our bathers. I became a little excited when I saw my sister and Sue completely nude. I hadn`t previously known that between their legs would be an area of dark hair. My eyes almost popped out at the sight of their lovely breasts.

Tom said "I`ve often seen Sue quite naked but never Ruth. I`m affected by it."

Sue chuckled and said "I can see how affected you and Fred are. Your pricks are growing."

"That`s true" said Tom. "How do you feel, Fred, seeing Sue and Ruth with nothing on?"

"I like it very much and hope that Ruth and Sue aren`t embarassed at seeing me naked."

 "I`m not but what about you, Ruth?" Sue asked.

"Neither am I, but Tom said he`d seen you naked several times so I don`t suppose he`s embarassed at seeing me naked."

"I`ve seen Tom with his prick quite hard. You haven`t ever seen Fred naked before so you haven`t seen him with a hard cock. Would you like to see it like that?"

"Yes, I would, but what do you think about that, Fred?" asked Ruth.

"Well, I suppose it would be alright, but I`d have to stroke it to get it hard."

"Go ahead, then" said Sue. "Show us what it`s like when it`s hard."

Both Tom and I stroked our cocks and got them fully hard, at least as hard as a 16 year old boy can make it. I knew that I mustn`t continue stroking. When I tossed off (as I called it in those days) I would ejaculate something from my cock. It wouldn`t be right for that to happen in front of my sister and Sue.

"I`ve never before seen Fred and Tom naked and now I can see both of their pricks hard. I must say I like it. Can you make yours harder, Fred?"

"No."

"Of course he can`t," said Sue. "If he strokes any more he will cum. The same with Tom.

I`ve seen him masturbating and cumming several times."

"I`ve never seen Fred doing that. I didn`t know what it was but you`ve just told me. I`d like to see it happening to Fred and Tom. Would you both do it and show me?"

"I will," Tom said. "I`ve done it in front of Sue several times. What about you, Fred?"

"I`ve never done it when Ruth was around but she wants me to do it so I will."

Both Tom and I continued tossing off (or masturbating to use the word Sue used). It seemed to me that my sister was looking more closely at me than at Tom. I realised that I liked my sister seeing me naked and masturbating. My cum soon fell on to the tiles round the pool as did Tom`s.

"Well done. I liked seeing you two boys cumming like that. Did you, Ruth"? asked Sue.

"I did. I`ve never before seen it being done and now I`ve seen your brother and mine cumming. Can we see it again now?"

"No, but I can do it again tomorrow," I said.

"The same with me," said Tom.

The next day Ruth and I went next door and met Tom and Sue. We all took off our bathers. Now, though, things went differently from the day before. Sue said that that she and Tom had been talking and she wondered if Ruth and I would do what she and Tom sometimes did. When Ruth asked what it was, Sue`s reply was that she and her brother masturbate each other.

"What do you think about it?" Ruth asked me. "All I have to do is stroke your cock. You`ve never masturbated me and I`d like you to do it."

"I don`t know how to do it."

"I`ll show you." she replied. "Come over to me," she replied.

Ruth gave me a lesson. Taking my hand she put it between her legs and told me to put my middle finger into her pussy, as she called it. Then told me to probe in there until I felt something. When I did she said it was her clitoris and I should caress it, so I did. Meanwhile she was stroking my cock.

I looked at Tom and Sue and saw they were doing the same, he with his fingers in her pussy (or cunt as I now know it). I heard Sue crying out that she was cumming and I could see that Tom was, also cumming. Ruth gasped out that she was also cumming, and so was I.

"Now that you and Ruth have done that to each other, did you enjoy it?" asked Sue.

"Very much. It was the first time for both of us" Ruth replied. "We really must do it again tomorrow."

"You don`t always have to do it here. You can do it in your garden if you want." Tom said.

We did, in the garden and by the pool. Several times before the weather broke. Since then, I`ve wondered why we only masturbated and not fucked. Perhaps we were too immature.