Blake Lively is all smiles on the cover of People magazine. She became a mom just last month, but has been primed for the job for years.

“I’m always teasing my sister’s kids that they are my own, and I’m always taking care of other people’s kids,” says the star, who welcomed her first child with husband Ryan Reynolds in December. (At press time the new parents had not yet revealed the baby’s gender or name.)

“Maybe because I didn’t grow up with little siblings, I’ve been making up for lost time. I’ve always felt like a mama.”

Now that she actually is one, “I don’t feel like it’s a massive change. I’ve always wanted a big family, and I understand that feeling when you have your first kid of ‘Let’s really be present in this.’ I do want to just enjoy this moment.”

But? “But I also feel like my first child is going to be the oldest sibling to the next kid, and that may change with each and every year. You don’t just raise your kids, your kids also raise each other – oh my Lord, the things I learned from my brother Eric. He’s influenced my life so much. So I’m looking forward to how one baby influences the other, and to my family as a whole, to every single chapter.”

Co-star and close friend, Amber Tamblyn was one of the last to find out. Tamblyn told People magazine that when she went to visit Lively, she had no idea there would be a baby present. “I went up there and I didn’t know, everybody knew but me, and she does that shit to me,” Tamblyn said. Apparently, Lively texted Tamblyn about new wallpaper that she was anxious for her friend to see. But that wallpaper turned out to be a newborn. “And I went up there, and there was her baby,” Tamblyn said. “That bitch! She tricked me!” Tamblyn joked.

Tamblyn said that all of the “Sisterhood” girls have seen the baby. “I’m very excited for her and Ryan, and to be an auntie,” Tamblyn said. “All of us are godmothers, so we are very happy.”