"Jon & Kate" Plus Nine - A Mistress?

Things are about to get more complicated on the set of the reality show, "Jon & Kate Plus Eight".

Sextuplets and twin girls made "Jon & Kate Plus Eight" one of the most loved and watched families in America.

Now, there's scrutiny against husband John Gosselin over an alleged affair. Us Weekly is reporting in its latest issue that he has been cheating on his wife with 23-year-old Deanna Hummel, a third-grade teacher.

"She's convinced he's going to divorce Kate for her," said Lindsay Powers, staff editor at Us Weekly.

It's no secret to loyal viewers that their eight children have put enormous strain on Jon and Kate's relationship.

"Kate is often promoting her book, "Eight Little Faces," about their family. And Jon, he's been really out on the club scene lately," Powers said. "So when he's not with his kids and Kate's traveling, he's sending $3 shots to this woman he's having an affair with."

Deanna's older brother, Jason, told Us Weekly that Jon, 32, was relentlessly pursuing his sister.

"He tells us that on one of their first dates, Jon came over with a half eaten pizza box and a bag of chips and they spent their whole night together in her room acting like, quote, a couple of teenagers," Powers said.

According to Us Weekly, "while TLC had no comment on the story or the couple's marital status, Jon sent an e-mailed statement to Us."

"I went to Legends to speak to the owner. A friend of mine wanted to check out my car, so I let her drive it to her car," he says. "Yes, I have female friends -- but that is all she is. I'm not going to end my friendships just because I'm on TV."

He made additonal comments to "Extra" as well.

"However, being out with them late at night showed poor judgment on my part, he told "Extra". "What makes me sick is that my careless behavior has put my family in this uncomfortable position." Gosselin says, "My family is the most important thing in my life and it kills me that these allegations have hurt them."