One of the cardinal rules of dating is never go out with a friends ex. This rule is broken all the time, and while those friendships are often left hurting a result, over time those wounds can heal. But when your sibling starts dating your ex, that’s when things get really weird. Aside from the obvious gross factor, there’s the potential ripple effect that could cause the entire family to choose sides, not to mention making the always awkward Thanksgiving dinner even worse. Here are the stars who tossed taboo to the wind and got involved in love triangles within their own family.

Hugh Hefner dated Karissa and Kristina Shannon at the same time

While it’s arguably gross for anyone under the age of around 60 to be dating Hugh Hefner at this point, the elderly Playboy founder took cradle-robbing to a whole new level when he dated twin sisters Karissa and Kristina Shannon at the same time. In October of 2008, Hefner found comfort in the 19-year-old twins in the wake of his breakup from the original The Girls Next Door stars, Holly Madison, Kendra Wilkinson, and Bridget Marquardt. The Shannon twins stepped into The Girls Next Door vacancy alongside Crystal Harris, who Hefner eventually married, so regardless of the innate nastiness of two sisters getting in on with the same old dude, they did somehow manage to help him transition to monogamy, since he’s still married to Crystal Hefner as of this writing.

According to Karissa, the twins found Hefner’s first rule of the mansion a tad difficult to follow. “We were not allowed to have boys in the house. That was the absolute number one rule – no boys allowed. That was one of the main reasons we moved out. But living there and being seen out with other guys, Hugh was tripping,” she told The Sun (Via Contact Music). Hugh was nice enough to let them live in the guest house before eventually sending them packing for good in May of 2010, after which Karissa confirmed to The Celebrity Cafe what literally everyone had already speculated about this whole scandalous romance. “It’s a whole new life. I went to Monte Carlo, Ireland, Italy; I went everywhere. I got TV shows, a lot of experience, and stuff like that. I did a lot more covers for magazines. I did a commercial for Guitar Hero. There’s just so much stuff and opportunities, it’s just crazy,” she said. Sounds like true love.