Benji Madden’s new girlfriend, Playboy’s former Girl Next Door Holly Madison, is having some difficulty breaking the ice with the rocker’s future sister-in-law, socialite Nicole Richie.

Nicole, who is dating Benji’s twin brother Joel, hasn’t bonded as well with the buxom blonde as she has with Benji’s past girlfriends — especially former fiancee Sophie Monk, who was a frequent shopping companion for the mother of two.

“Benji is way more than a brother-in-law to Nicole, they are actually very good friends too and he respects her opinion,” a family friend tattles in Jan. 4 issue of The Daily Mirror. “While Nicole doesn’t dislike Holly per se, she just doesn’t seem to have anything in common with her and isn’t sure she’s the right girl for Benji.”