Robbie gazed at his sister's body. Her stomach was flat, her breasts jutted upward and were pushed up by her bikini top. Her cleavage, in this position, looked magnificent. He felt his cock stir in his swim trunks. Her ass was so perfectly encased in those tiny denim shorts. He wondered what it would be like to peel them off of her. He thought back at some of the things he had done with Renee - things that she had loved - and wondered how his sister would react to those things. He knew that she had absolutely no experience with sex. He needed to stop thinking about that. Then...