Caleb Followill and Lily Aldridge
Rabbani and Solimene Photography/WireImage
04/24/2011 at 11:00 AM EDT
Kings of Leon singer Caleb Followill says he doesn't know the exact date of his wedding, but he seems certain that he will marry his Victoria's Secret model fiancée Lily Aldridge
"You have to ask Lily [about the wedding date]. She won't tell me. I think it's somewhere between May 10 and May 20, but she won't tell me because I have a big mouth," Caleb told PEOPLE recently at the Tribeca Film Festival premiere of his band's documentary, Talihina Nights: The Story of Kings of Leon
Caleb's bandmate brothers Nathan and Jared Followill, however, are more forthcoming when it comes to the specifics of the wedding.
"It's going to be a very small wedding and then a big party," Jared said. "I think there are only like maybe 25 people or so going to the wedding, but a lot of people will be at the party."
"I'm the best man," Nathan added, "and they're having lemon custard for their wedding cake."
Nathan, who wed Jessie Baylin
in 2009, has this advice for Caleb: "Don't get married!"
Jared, however, assures PEOPLE that Aldridge has been welcomed into their family with open arms. In fact, the "Sexy Little Bride" model
can be seen on tour with the guys throughout the documentary – and she was practically inseparable from the brothers' mom at a Heineken-sponsored afterparty for the film.
"We love her! I'm so excited for the wedding," Jared said of his sister-in-law-to-be.
And while Aldridge seems to be firmly in control of all the wedding details, she should beware of the ulterior motive of her groom's brother.
"I just hope she invites all of her model friends [to the wedding]," Jared said. "That's the only reason I'm going."