Harlow Winter Kate Madden won't be a year old until Jan. 11, but her uncle, Benji Madden, already has a warning for potential suitors.
"I'm going to be keeping a close eye on her," Madden, 29, tells PEOPLE of the daughter of twin brother Joel Madden and his girlfriend Nicole Richie, 27. "I'll leave the shotgun right by the door."
Says Madden, who rang in the new year in Las Vegas at Hard Rock Hotel's Body English, "We're lucky being twins, because Joel can be the good guy and I'll be the bad guy."
The Good Charlotte guitarist is thrilled with the way Harlow's parents have been raising her so far.
"When they had her, their instincts just kind of came out, and it's amazing to see," he says.
What makes it work? Harlow comes first, says Madden. "They just really put their child above everything."
Adds Madden: "Joel is such a great dad and Nicole is the best mom I've ever seen. Joel is all about showing up. His main concern in life is protecting and caring for his family."