Being a dad to kids AVA and DEACON comes naturally to RYAN PHILLIPPE, he says in an all-new ET interview.

"Being a father is by far my greatest achievement and the most important thing about me," he tells our THEA ANDREWS. "My mother had a day-care center in my house growing up. And I come from a big family on the East Coast. We grew up helping take care of and raise kids, so it's very second nature to me."

After his split from Oscar winner REESE WITHERSPOON, however, he faced unusual parenting challenges, such as trying to explain to his kids who the paparazzi are.

"You try to make it seem as commonplace as you can. That's sort of the approach you have to take with all of that stuff, with the press, with the paparazzi. You kinda just say, 'Well, you know, Mommy and Daddy do this certain kind of job and it creates an interest in the public,' and you minimize all of that stuff as much as you can."

Now, he's talking up his new movie, 'Stop-Loss,' in which he plays an Iraq war hero who struggles to return to civilian life back in his Texas hometown. He says he can relate because he nearly enlisted to be a soldier himself.

"Out of high school, I didn't have a ton of options because my grades weren't the best and I don't come from money," he says. "When I graduated, it was around the time of the first Gulf War and I did go and sit in a recruitment office and I ended up getting the T-shirt and everything. And the guy who went in with me ended up going over and serving in the first Gulf War, but I went to New York to be an actor instead."

'Stop-Loss' also stars ABBIE CORNISH, CHANNING TATUM ('Step Up') and CIARAN HINDS. It opens in theaters on March 28.