Ask Ventimiglia in what ways he's most like Jack and he'll start off with their differences.
"I'm not an alcoholic, so I don't think I'm like him in that way," he says. "My parents didn't drink, and it was never anything I was raised around, so it just, it never factored into my life ... How we're alike? I'd like to think I care about the people I love, like Jack does."
But more than living up to a fictional character, Ventimiglia is trying to fill the shoes of his parents -- his mother, Carol, a retired teacher, and his father, Peter, a Vietnam veteran who was in the printing business before he retired.
"I still want to be my dad," he says, flashing his signature crooked smile. "Growing up, my father represented this person of strength, of character. I saw not only the way he would talk to other people and his family but also how people would talk about him. People love my father -- people love my mother. For me, it's always been, 'I want to live up to that.'"
Amy Sherman-Palladino, the creator of "Gilmore Girls" and a longtime friend, can attest that he does -- and not simply because he's the one who persuaded her to stop consuming energy drinks.
"If you know Milo the way I know Milo -- I always say that I could never have kids, because I could never be guaranteed that they would turn out to be Milo," says Palladino, who sees Ventimiglia more frequently on the red carpet as of late thanks to her new Amazon series, "The Marvelous Mrs. Maisel." "He's always been such a stand-up guy. He's so kind. He's so thoughtful of everybody and so gracious to his co-actors and his crew. He takes his work extremely seriously without taking himself extremely seriously."
Mandy Moore, who plays Jack's wife, Rebecca, on "This Is Us," says Ventimiglia is Peak Dad in the little moments. She offers a time, before production on the first season had begun, when the two were set to make a press appearance and a strap on her shoe broke.
"He pulled out a pocket knife and, like, MacGyver-ed the thing and was able to tie the piece back on on my foot and made the shoe work," she says by phone. "He's that guy."
Ventimiglia's road to becoming America's TV dad has been a winding one, starting at age 8 -- the age he knew he wanted to be an actor. Growing up in Anaheim, Ventimiglia would put on plays with his two sisters in the family living room -- he recalls coming up with plays inspired by the 19th century children's novel "The Water Babies."
"I remember watching the Academy Awards with my mom and dad as a kid and seeing the acting clips (and) thinking, 'That's what I want to do,'" he says. "But I didn't understand that it could be a career. I just knew I wanted to do it."