Austin Nichols admits he felt "weird" kissing Mary-Kate Olsen in 'Holiday in the Sun' because he was "too old" compared to her

And, because of the age gap, Austin felt uncomfortable when he had to give Mary-Kate, 38, a smooch in Steve Purcell's 2001 flick.

Speaking on the 'Drama Queens' podcast, he admitted: "I was definitely nervous because Mary-Kate was 15, and I was, I think, 18 or 19, or maybe even 20.

"I don't remember, but I was too old. And it felt weird, and it felt wrong.

"And I looked very young, so watching the movie, I don't think you notice. I'm real tall and skinny and nerdy.

"But I don't think you can tell there's a big age difference. But from my brain, I was like, 'She's 15. This is weird.'"

The 'One Tree Hill' actor was so concerned about the moment, that he had to ask Mary-Kate and her twin Ashley Olsen - who played Madison's sister Alex - dad David and the flick's producers if it was OK to kiss her.

Austin recalled: "So, I remember talking to producers, and I remember talking to even her dad was there.

"And I just wanted everybody to - I was like, 'Is this OK with you guys?' And they were all like, 'Oh, don't worry about it.'

"Nobody seemed concerned. And I was very concerned, but it turned out fine. It was all very G-rated."

Mary-Kate and Ashley played wealthy teenagers who jetted to the Bahamas with their parents for a winter getaway

While Austin's character tried to woo over Madison, Ashley's alter ego fell head over heels for resort worker Jordan Landers, who was played by Ben Easter.

And he was also "a little bit nervous because of my age".

He told E! News in 2021: "I was a little bit nervous because of my age. My manager was like, 'I think they told the girls you were 16.'"

Ben immediately told Ashley he was almost 22.

The now photographer continued: "We hit it off right off the bat. They could see I was professional, and I wasn't some creep."