Asked by PEOPLE on Tuesday about Paltrow's prediction that the kids will get married one day, McGraw replied: "That's what I hear. That's what I hear. Well, he better make a lot of money!"
McGraw, 43, was speaking at a special screening in Los Angeles of Country Strong, in which he and Paltrow both star. The two families grew close while filming in Nashville – and Gwyneth and Faith developed a good friendship, says McGraw.
"They just enjoyed each other," he says. "The kids really had a great time, and we all had a lot in common."
Paltrow and Hill would even head out together in the evenings, leaving McGraw to hold down the fort with his three daughters.
"I babysat the whole time," he says. "Faith and Gwyneth went out and partied. I didn't get to go out. … I was tired! So they went out. They had a good time."