Good Charlotte singer Benji Madden has flown to Sydney with Australian actress and pop star SOPHIE MONK to spend the holidays with her family. Madden, 27 and Monk, 27, have been dating for several months and things seem to be getting serious. A source says, "Sophie and Benji really like each other. They balance each other quite nicely. "This trip is just taking it to the next level in their relationship. Plus, it's summer time in Australia right now - they've been having a great time." Monk has appeared in the Adam Sandler movie CLICK and has previously been linked to British stars Jason Statham and Jude Law. Madden is the twin brother of Joel Madden, who recently ended his relationship with Hilary Duff and is now romantically linked to Nicole Richie.