Credit: Courtesy of Larry Birkhead

Four years after Anna Nicole Smith's tragic death, Us Weekly caught up with Larry Birkhead, who's raising 4-year-old Dannielynn all on his own.

"Dannielynn knows that her mom passed away. She obviously doesn't know the details," he tells Us. "At first I said, 'Your mommmy's up in the clouds.' Then we were on a plane from Kentucky and she asked, 'Which cloud is my mom on. Maybe she can come play?' You have to be forthright but keep it on a kid-friendly level."

Still, life as a single parent hasn't been easy for Birkhead, 38, who was granted custody of Dannielynn in April 2007 after a dramatic paternity suit with Smith's partner Howard K. Stern.

"It's hard to flip from friend to parent. I overcompensate because she doesn't have a mom and I probably give her more than I should," he tells Us. "I'm working on cutting down on the shopping sprees."

For more on Birkhead and Dannielynn's life without Smith -- including how they plan to spend Father's Day together -- pick up the new issue of Us Weekly, on stands now.