Vocalist Joel Madden's lyrics for this song are about his first child Harlow Winter Kate Madden, who was born January 11, 2008. His brother, guitarist Benji Madden told Spin magazine: "I got chills the first time I heard it. I could tell he meant every word. It's really cool to see my brother digging deep and writing from the heart. When Joel told me he was going be a Dad, I was psyched. Joel? He's the rock star! When you see Joel step on stage… he's born to be a rock star. But he's also the best father I know. He wrote about the love he has for his kids and his girl Nicole [Richie]. He's really found himself through his family. When I have a family - and I definitely want to - I want it to be like his."
Originally, Joel intended this song to be a lullaby just for his daughter, but Benji loved its raw emotion and insisted it went on the album. Joel explained to PopEater that his new role of parent influenced the writing of the album. "[There's] a song that I wrote for my daughter called 'Harlow's Song,' and it was originally like a lullaby, and then [Benji] heard it and really liked it, and the guys heard it and they all liked it," Joel says. "I've never written a song like that. It was pretty interesting. It's like a straight love song for somebody. It's a lullaby, and it ended up being on the record. I've never really had the ability to write songs like that. So I guess my life has changed a lot."