Billboard Bits serves up the best bite-sized nuggets of music news and gossip.

Christina Aguilera No Longer Living With Both Ex-Husband, New Boyfriend

Life just got a whole less awkward for Christina Aguilera. Recent reports claim that until yesterday (Jan. 4), the singer was sharing her Beverly Hills home with not only her ex-husband Jordan Bratman and their son -- but also her new beau, Matthew Rutler. Rutler reportedly moved in several weeks ago, and yesterday, Bratman finally moved out. (TMZ)

John Mellencamp and Meg Ryan Dating?

Although it was just announced last week that John Mellencamp and his wife of 20 years were calling it quits, the Indiana rocker supposedly has a new female companion already -- actress Meg Ryan. The two were first spotted together in NYC in October, and recent reports indicate claim they are, in fact, dating. However, sources claim that the romance began well after John and Elaine Mellencamp decided to divorce. (Rolling Stone)

Will Ferrell, John C. Reilly Recording 'Step Brothers'-Inspired Rap Album

According to a tweet from longtime Will Ferrell collaborator Adam McKay, we may not have seen -- or at least haven't heard -- the last of "Step Brothers" characters Brennan Huff and Dale Doback. "I wasn't kidding about Step Bros rap album. And we just found out we have a crazy big time producer. Mos Def, you up for a guest flow?" McKay tweeted Tuesday (Jan.4). This undoubtedly stems from an oft-quoted scene from the 2008 film in which Huff and Doback (played by Ferrell and John C. Reilly, respectively) premiere their rap song "Boats 'N Hoes" to bemused onlookers. ( Popeater)

Collaborations Abound in Rock World

Two elder statesmen of rock announced collaborations with decidedly younger (than them) musicians this week. Dave Sitek, producer and guitarist for TV on the Radio, has officially joined '90s rock mainstays Jane's Addiction as the band's bassist. Sitek, now a member of the band's "creative team," will be performing on and writing for the act's forthcoming, in-progress album. In addition, Robbie Robertson of rock pioneers The Band announced an upcoming collaboration with Trent Reznor and Rage Against the Machine guitarist Tom Morello. Robertson will be releasing an album in April titled "How to Become Clairvoyant," and the record -- his first in 13 years -- will include contributions from Reznor and Morello. ( L.A. Times, The Guardian)

Damon Albarn, Sonic Youth, Members of Flaming Lips and Vampire Weekend Score Films

Following in the footsteps of "Tron: Legacy" score composers Daft Punk, four notable acts announced film score releases this week. The score of the Jude Law short film "The Boy in the Oak" will be receiving treatment from Blur/Gorillaz frontman Damon Albarn, while The Flaming Lips multi-instrumentalist Steven Drozd will be handling the music for documentary "The Heart is a Drum Machine." In addition, it was reported earlier this week that Vampire Weekend's Rostam Batmanglij was at the helm of the score for upcoming film "Sound of My Voice," while Sonic Youth had handled French flick "Simon Werner a Disparu." (Pitchfork)

(Reporting by Jillian Mapes and Kevin Rutherford)