Katherine Heigl Gushes Over Her Marriage to Josh Kelley and How Her Daughters Have Embraced Being Big Sisters

"I have this philosophy that once you have more than one, whether it'd be a dog or a horse or a child, it's all the same," she told E! News

Katherine Heigl knew she wanted a big family with husband Josh Kelley, possibly even before their eldest child was born.

The 38-year-old actress, who will celebrate her 10th wedding anniversary with her husband this December, opened up to E! News about the couple's relationship and life with their three kids.

When asked what is the secret to having a long-lasting relationship, the actress said, "I have no idea! I think honestly, that we just are really good friends. I think this is the first relationship where I've felt like my partner's more than just my lover, if you will, and is a friend as well. We're sort of best friends, we get along really well, we have a really good time together. We have our moments, like any couple, so we just sort of cling to that friendship when stuff gets hard."

My morning snuggle buddies! ????????My favorite way to start the day is with these three! #morningbliss #savoreverymoment #thoseheavenlydays

A post shared by Katherine Heigl (@katherineheigl) on Apr 5, 2017 at 12:04pm PDT

Heigl and Kelley share adopted daughters Naleigh, 8, and Adalaide, 5, and son Joshua, who the actress gave birth to four months ago.

"I have this philosophy that once you have more than one, whether it'd be a dog or a horse or a child, it's all the same," Heigl told E! News. "So I'm kind of like, 'Let's have four or five' and Josh is tapping out."

The actress and her family live on a ranch in Utah with several pets, including dogs. On Easter Sunday, Heigl shared on Instagram a photo of the group standing near their horse Bellaco. 

Heigl said their daughters are "great" with their son.

"Adalaide has become such a little Mommy," she said. "She's carrying around her baby doll, she's changing her baby doll's diaper, she's talking about how much work her baby doll is, how much pressure it is to raise her baby doll right. They're fawning all over him. The kid's a really jolly little guy and my mother keeps saying, 'Why wouldn't he be? He eats all day, he sleeps all night—which is a total blessing—and he's fawned on over by women all day, every day."

Heigl made her comments at the premiere of her newest film, the thriller Unforgettable Tuesday. Kelley joined her at the event and the two showcased some PDA.

Unforgettable is set for release Friday.