Justin Timberlake will marry his girlfriend Jessica Biel, according to source.

Having dated since January 2007, the SexyBack singer has asked his actress lover to move in with him, which proves just how serious he is.

“Jessica is preparing to live in Justin’s Hollywood Hills home,” an insider tells In Touch. “They’re both really excited.”

The former N Sync star, who dated Cameron Diaz before embarking on a relationship with Jessica Biel, has never asked a girl to move in with him, but the insider insists he’s ready: “They’re definitely headed for marriage. Moving in is just the beginning.”

The source also explains how the two lovebirds have managed to make their relationship work: “They avoid the spotlight as much as possible.”