I was sitting on the couch one time, when my stepdaughters were younger, and they were sitting in front of the couch with my two kids by a coffee table. The oldest (K) starting acting weird, moving around, and then finally came and sat on the floor right at my feet. Her behavior was very suspicious, but I couldnt figure out what she was up to. Later, after the kids had gone outside to play, I realized there was a hole in the crotch and since I wasn't wearing any underwear, my balls had been visible depending where you were sitting. I was very surprised that she had been interested enough to come all the way over and get a better look, I chalked it up to normal curiosity.
It was a few years until the next incident, I was getting ready to take a shower and I was standing naked in the bathroom. I had the 'turtle effect' going on, so I pulled the skin on my penis back to free the head, and then I pulled some of the public hair out of the way. I caught movement out of the corner of my eye. The bathroom was in the master bedroom, so I hadn't bothered to close the door, it was slightly ajar. Curious, I peeked out into the bedroom and saw 'K' slip out into the hallway. Again, I was really surprised she had snuck in there to look.
A few more years went by, and she developed into an attractive young woman. One night I leaned in to hug her goodnight, and accidently cupped her breast in my hand. When she saw how horrified I was, she laughed. I went into her room the next morning to make sure we were 'cool'. Her sister was still asleep, and K was curled up on top of her bed wearing only a t-shirt. She had gold panties on, and made no effort to cover herself. Other than that, nothing else odd really happened.
Then came the Florida vacation. Everyone else was out at the pool, and I was in the room, soaking my sore feet. 'K' came in the room for some reason or the other. I don't remember exactly how it happened, but she ended up rubbing my feet for me a little bit. There was nothing odd about that, except she stared at my crotch the entire time. I had on boxer-briefs, which I often wore around the house in front of the kids, without really thinking about it. Her stare was making me get really hard, which was fairly obvious, but she just kept staring like nothing was out of the ordinary. She actually got up on her knees, in between my legs, and made a show of massaging my thigh, all the while looking right down at my crotch. I was sure my wife (ex-wife, now) or another kid would come in soon, so I told her she should go back out to the pool. She got up, and asked if I was coming. I told her I needed to change into my swim trunks, and she said she would wait for me. I thought about going into the bathroom and leaving the door open, giving her a chance to peek if she wanted to, but my **** was hard (which always leads to bad choices). I just dropped my underwear right in the room, acting like nothing was out of the ordinary. My hard **** was standing at attention, right in full view of my stepdaughter. She looked right at it for a minute, her mouth handing open, and then turned and left the room quickly. I put on my trunks and went out to the pool, after waiting for my erection to die down, and she acted like nothing happened.
That was the last time, she is married and moved away now.