Kristin Cavallari Explains How She Met New Young BF Mark Estes

It's not quite "How I Met Your Father" -- not yet, anyway -- but Kristin Cavallari's explaining how she bagged her much younger boo, Mark Estes, and like most things these days, it started with her scrolling.

Kristin spilled the tea on her 'Let's Be Honest' podcast ... she says she was casually watching TikTok vids in September, when she stumbled upon Mark's group Montana Boyz, and he caught her eye as the hottest one.

She then moved on with her life -- until fate swooped in 3 weeks later, bringing them together.

Kristin said she randomly got a DM from one of the Montana Boyz saying, "I love you" ... and she was so excited by the digital flirtation, she invited them to her podcast.

As Kristin was setting up the interview, her assistant dropped the bombshell the Montana Boyz were moving to Nashville ... right where Kristin lives! How convenient.

It's like the stars aligned or something.

Kristin kept the DM convo alive ... telling them she'd take them line dancing when they were in town -- before asking who in particular she was talking to. When she found out it was Mark, she responded, "Oh good, you're my favorite!"

Once together, the pair wasted no time ... going on a date just before Valentine's Day, and Mark even met Kristin's kiddos, who she shares with ex-husband Jay Cutler.

Right after their date, they started hanging out a whole lot more, and next thing you know, they were jetting off to Cabo together -- around the time their romance came to public attention.

At 37, the reality star adds that dating a 24-year-old wasn't part of her grand plan. Age is just a number, after all!

She's certainly head over heels for her man ... commenting "smash" on a recent IG thirst trap of him. Might just be the real deal, folks!