Vince Vaughn's new role as Santa Claus' brother in new movie Fred Claus has upset his young nephew - the four-year-old is angry his uncle hasn't introduced him to Father Christmas. The actor's nephew spotted his Uncle Vince on a poster for the seasonal film and immediately wanted to know how long Vaughn had known Santa Claus. Vaughn says, "My nephew Dexter saw a (Fred Claus) poster of me. My sister's really upset with me because he's four and obviously she wants to keep the Santa Claus thing going. "And he was like, `How does Uncle Vince know Santa Claus? And why hasn't Uncle Vince introduced me to Santa Claus?' He thought I was holding out on him." But Vaughn has discovered a benefit to knowing Santa personally - his nieces and nephews fear he's got a hotline to the North Pole. The Wedding Crashers star adds, "I like to be the fun uncle, I don't like to discipline anybody. But when you get some of them together, if they don't share toys, sometimes you're forced to lay down the law. So now I'll say, 'Listen, I know the big guy. Don't make me call him, don't make me stop the toy train that's going to happen for you guys this year.'"