Kristin Cavallari Is Open To Having Kids With Her New Boyfriend Mark Estes

Kristin Cavallari may be a new mom in the future -- at least that's what she's saying ... 'cause her boyfriend wants to have kids.

The reality star explained on her "Let's Be Honest" podcast that her 24-year-old BF, Mark Estes, has his sights set on being a dad -- and because of this, she's been mulling over potentially popping out another baby with him, assuming everything works out.

So far it looks like Kristin -- who's currently 37 herself -- might be leaning towards expanding her brood ... even joking with her cohost her future little one could become so famous it'd be her one-way ticket into retirement ... 'cause the kid would be so freaking good looking.

Jokes aside, KC is giving it some serious thought ... saying her 3 other kiddos -- Camden, 11, Jaxon, 9, and Saylor, 8 -- are old enough to help out with a new baby. BTW, she shares those three children with her ex-husband, Jay Cutler.

Kristin admits she still hasn't figured out if Mark's the one, even though their romance has been on a good track since February.

Kristin recently posted a pic of Mark having a chat with one of her kids, so on its face -- she seems to think he's already showing fatherly qualities ... which might be why she's even talking about this.

Cavallari wasted no time going public with her relationship with Mark after TMZ posted cozy photos of them hanging out down in Cabo 2 months ago.