Jennifer Lopez's children have made her grow up.

The 40-year-old singer-and-actress was unprepared for how much she would change when she gave birth to twins Max and Emme - her children with husband Marc Anthony - two years ago.

She said: "I can't help but be a different person now that I've had kids. That really does change your whole perspective on life for the better. I definitely feel like I've grown up.

"My main priority now is that my kids are happy; that's my number one focus in life. Are these little people happy, content, and getting everything they need? Everything after that is secondary. Before, my work was my main priority - even above myself.

"I think the biggest thing they've taught me is what loving someone is and what it should feel like. This is what unconditional love means. It's crazy, but it's heaven and earth."

Despite her happiness with her family, the 'Back Up Plan' star admits she feels an overwhelming sense of guilt whenever she has to go out without the twins.

She added to Redbook magazine: "I didn't know that feeling before. You don't know about it because nobody ever tells you. I think it's because women are a little ashamed to admit it. You feel guilty whenever you can't have your kids right there with you on your hip."