Dr. Paul Nassif and Adrienne Maloof on October 20, 2011 in New York City. Credit: Gary Gershoff/Getty Images

Another broken Housewives household.

As suspected, Real Housewives of Beverly Hills' Paul Nassif has filed for legal separation from wife Adrienne Maloof. The plastic surgeon and hotel mogul have been married for nine years and share three young sons, Gavin and twins Colin and Christian.

Filing the documents in an L.A. County Superior Court Monday morning, Nassif told TMZ: "The welfare of our children is my primary focus as Adrienne and I work through this difficult time. I want the best for her and our children and I hope that everyone can respect our privacy away from the cameras."

Friction between the couple was never exactly a secret to fans, as their sometimes uncomfortable bickering was a common focus on the Bravo hit. "There is a lot of anger and frustration. It's all the stuff you saw on TV," a family friend of the couple tells Us Weekly. "They fight constantly."

Adds the friend: "It was a very volatile relationship. But they are trying to keep it civil for the sake of the kids."

Tell Us: Are you sad about the split?