This is a story in the Collar Club.
A frustrated man cheats on his wife with a hooker, surprising her pleasantly with his dominant ways. Their weekend is rather enjoyable, as it turns out.
Beautiful young girl seduces her twin brother. They continue to make love. She forgot to take her pill and ends up pregnant. Her BFF from high school makes love with him at college while she is at home with her pregnancy.
Party girl Lexi is looking for someone who can make her feel a spark. Someone mature, hot, and fun. And she finds her brother, looking for the same thing.