"Benji proposed to Sophie in Australia on Christmas Eve with a Neil Lane diamond ring," Monk's publicist told People magazine.
The couple was spotted in December canoodling in Los Angeles in September, Extra TV reported.
Monk has appeared in such films as "Date Movie" and "Click" and stars in the comedy "Spring Breakdown." Madden's rock group will release its next album in March.
Celebrity Families of 2014 [PHOTOS]