Kristin Cavallari and Mark Estes' romance is "very serious"

Mark told Us Weekly: "It's very serious. I'd say as serious as it gets."

Mark also insisted that he isn't bothered by their 13-year age gap.

He said: "I don't dive too deep into that. People are going to talk no matter what you're doing. I just brush it off my shoulder and if it makes me happy, that's what I'm going to do."

Mark stars alongside Kaleb Campbell Winterburn and Kade Wilcox in the TikTok famous Montana Boyz.

And Mark's co-stars are proud of how he's handling his new-found fame.

Kade said: "It's tough. There's a lot of people that hate on it.

"I mean, we know him, and he knows himself."

In March, Kristin insisted she wasn't "searching" for a younger man when she met Mark.

The blonde beauty defended their 13-year-old gap, revealing that she wasn't consciously looking for a younger boyfriend.

She said on her 'Let's Be Honest with Kristin Cavallari' podcast: "I want you guys to know that me dating a 24-year-old is not something that I was, like, searching out.

"If you guys listen to the podcast, you know, I thought 30-year-olds were too young for me. I understand what it looks like to the outside world, I really do. I get that."

Despite this, Kristin insisted that Mark isn't a "typical 24-year-old" man.

She added: "When I met him, I was like, obviously I thought he was the hottest guy I've ever seen. There was ... that attraction was always there. But when I met him I was like, he's actually a really nice, good guy. He's very sweet - from the jump, he was so sweet to me."