Hilary Duff is obsessed with her baby girl, Banks, but there was a moment before her birth that Duff had reservations.

This hesitation sparked from her son, Luca’s disappointment with having a little sister.

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“The guilt that I felt for bringing her into the world was so big,” Duff told PureWow on Wednesday. “It was just he and I for so long that he was like, ‘WhyWhy, Mom? Why would you do this? I really just love the way it is.’ And it wasn’t bratty, it was just so sad.”

“I was like, ‘How do I reverse this? It’s too late now,'” she recalled. “It’s such big feelings. When you’re pregnant, everything just feels more magnified.”

Fortunately, all that changed once Banks came into the world. Now, Luca is “100 per cent obsessed” with his baby sister.

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“It’s the best,” Duff gushed. “It’s a chemical reaction between siblings sometimes where he knows he has to protect her… It’s really sweet the way he looks out for her. But also, sometimes I’m like, ‘Hey, I did okay with you. I promise I know what I’m doing.’”

Duff shares her son, Luca Cruz Comrie, 7, with her ex-husband Mike Comrie and she shares Banks Violet Blair Koma, 1, with new hubby Matthew Koma.