Stan Walker, Karen's third husband (little is known about her first two), an unseen character. An obese man, Stan has worn a toupee since his teens. Stan has two children from a previous marriage to a woman named Kathy. Karen fell in love with him in the 1980s but they didn't marry until 1995. Jailed for tax evasion in season four, Stan began an affair with a cafeteria worker named Lorraine (played by Minnie Driver) and - after his release in season five - continued the affair, ultimately separating from Karen because of it. He died at the end of season five, but at the end of season seven he revealed himself to Will. He had faked his death and was hiding out with the aid of the government. He and Karen reconciled in season 8 but subsequently faced maritial difficulties and divorced. Stan's popularity with fast food establishments led to Pizza Hut taking out a full-page ad in the New York Times to congratulate him on his release from prison; Taco Bell also did a flyover at his funeral.

Mason Walker, Stan's son, another unseen character. He is known to Karen as "the fat one".

Olivia Walker, Stan's daughter, played by Hallee Hirsh. Although she has had fun times with Karen, such as sticking food to the floor to see how long Mason will spend trying to eat it, she also has problems with her stepmother.

Lois Whitley, Karen's mother, played by Suzanne Pleshette. A con artist who used Karen in her early schemes.

Virginia "Gin" Delaney, Karen's sister, played by Bernadette Peters. In 1963, as a child, she was injured in a brutal game of Twister with Karen.

Barry, Karen's cousin, played by Dan Futterman. Originally a gay bookish homebody, Karen had Will and Jack bring him out of his shell to become an attractive person who both Will and Jack fall for.