Kristin Cavallari sounds content with just having great sex with her younger boyfriend … even though he’s seemingly got an eye toward marriage and children.

The reality TV star was at LAX on Friday when photogs asked her if she and Mark Estes are having any serious discussions about starting a family together as husband and wife.

Kristin says they’re not having those conversations just yet, and she’s not looking for another marriage and more kids … at least at this point in their relationship.

Kristin’s already praised Mark for being the best sex she ever had … so it sounds like she’s happy with taking things slow and not rushing to the altar — or the delivery room.

Asked what her response would be should Mark pop the question … Kristin says she’s “not saying yes” and sees no need to get married again.

Mark’s 24 and she’s 37, and she says the “beauty of it” is Mark is so young he can get married in 10 years. Kristin’s divorced from Jay Cutler, and they have 3 kids together … so she’s already checked both of those boxes in her life.

It’s interesting to hear Kristin’s views on kids and marriage here … because back in April she said she was mulling over popping out a baby with Mark.

Worth noting … they’ve only been officially dating since February … so things could still change.