Her Butt

I have a really cute seventeen-year-old sister and live in a big house with a pool. Last weekend she was home alone and went for a dip. I came back from football training and saw her in her bikini splashing about in the shallow end.

I called her over from the verandah and she stood next to me leaning on the railings watching the sun twinkle on the water. Her bikini was hugging her buttocks and the water was dripping down her thighs. My cock started to rise and she asked, 'What's big bro all excited about, huh?' and shifted so she was leaning in front of me. She leant her butt back so it pressed into my groin, and we ever so softly slid together. I soon came in my shorts and she giggled as she went back to the pool.

I showered and since then we've done nothing sexual.