Ashlee Simpson may only be 24, but she's got one thing older sis Jess wants: a baby.

"She's always saying, 'Oh, I want a baby!' " Simpson tells October's Redbook, on sale Sept. 22. "Being a mom's so empowering and incredible. I'm one of those people who believes that life brings things to you at a certain time for a certain reason, and if you just go with it, that's where the best moments come from."

Having her son, Bronx, not only calmed down the once wild singer-turned-actress, it also helped her mature as a person, she says.

"I've grown up so much," she says. "Your body is changing, and it's such an amazing time to feel that connection ... Being pregnant was the healthiest I've ever been in my life. Except for the cupcakes."

When asked about whether she envies sister Jessica, 29, for her freedom as a single gal, Ashlee responds: "I really don't."