Also added to this domestic mix is the 2-year-old girl who Quaid's ex-wife, Meg Ryan, adopted in China, the star of the new movie Vantage Point tells USA Today.
"He's very bonded to Daisy," says Quaid of Jack, admitting that he too has gotten to know Daisy "a little bit" himself. "It's fantastic for Jack having a little brother and sisters now. He really wanted to have a little brother, and I really wanted to have a little girl, so we all got what we wanted."
Describing Jack as into "girls and school plays," Quaid, 53, also says his eldest is "definitely going to be an actor."
As for the two baby Quaids, "Having two is actually like having four," Quaid told David Letterman on the Late Show, "because you don't have enough arms, so we're looking into that." The sleep-deprived dad also noted that they seem to go "for the most dangerous things in the room."
A Princes and a NoisemakerIn terms of developing personalities, "They just discovered each other about three days ago. It was a great epiphany for them," Quaid told Letterman, who is the father of 4-year-old Harry. "She's like a little princess, she sleeps through the night, and he makes every sound known to man. It's incredible."
Quaid also showed their photos on his iPhone, which he said contains "a little 20 minutes' worth of slideshow." (When a shot of a French bulldog popped up on the phone, Letterman said, "Looks like you.")
Quaid also expressed how extremely grateful he and wife Kimberly were for the "happy ending" after the scare they received shortly after the twins' birth, when the children had to be hospitalized following a medication error. (The babies recovered, and the Quaids are pursuing legal action against the manufacturers of the blood thinner that was used.)
"The one thing that really came out of that for me, after a very horrific two weeks, is that I will never take another day for granted in my life, because if they hadn't made it, I never would have had another happy day in my life," Quaid told USA Today.
As tangible proof that Quaid is taking steps to live a better life, after attempting the feat for several years, he has finally given up smoking.
"I figured, I want to be around when they're 40, if I can," he says. "They stuck around for me, so I'm going to try to stick around for them."