Man Says He Busted Sister Having Sex With "Jon & Kate" Dad

The brother of the 23-year-old third grade school teacher accused of having a torrid affair with Jon & Kate Plus 8 dad Jon Gosselin says he busted the pair having sex.

John Hammel told US Weekly that he often heard his little sister, Deanna, having sex with the reality tv star.

"A lot of the time, it was pretty, um, gross listening to her, you know, um - how do I say this? The walls are thin. Let's just say that. I mean, no one wants to hear his sister having sex, let alone with a married dude who's, like, almost twice her age and who has eight kids and a maybe-crazy wife. Ick. Nast."

Hammel told the magazine that the pair met earlier this year at a Pennsylvania lounge where they sent each other $3 shots. He said that the father of eight began relentlessly courting his sister, and was a regular at their home by mid-February.  

Rumors that Gosselin was cheating on Kate exploded after a video surfaced online of the married TV dad leaving the home of his alleged mistress in March.

Hammel says the couple "pretty much stay locked away like two teenagers."  He also defended his sister, saying "She's a nice girl, not a homewrecker.  He is a bad liar ... this isn't healthy for her. But she is refusing to help herself, so here I am trying to help her myself. I hope this clears the air."

(Photo: WENN)