"When you're with somebody for 15 hours a day for three years, you get connected, and it's there forever," Patinkin told the Chicago Sun-Times' Sunday magazine, SPLASH.
"There's a part of me that loves being with her because I don't have a daughter. I love the pretend-ness of having a daughter.
"We're good friends. If you walked in the room, it's not Saul and Carrie having a cup of coffee. It's Claire talking about her baby and hearing stories about her family, my wife and I boring her and her husband with our past as parents, our journey as a married couple in show business," the Tony, Golden Globe and Emmy Award-winner said.
He and Kathryn Grody wed in 1980 and have two kids.
"I picked the right person," he laughed.
Homeland airs Sunday on Showtime.