By Jeff Nelson
January 02, 2018 at 08:41 AM EST

Pete Wentz and longtime girlfriend Meagan Camper are expecting once again — and it’s a girl!

The Fall Out Boy bassist, 38, and his model partner, 28, announced the happy news on social media New Year’s Day.

“Happy New Year! We’re kicking the year off with news of the best gift yet: 👧🏻 coming to our family in 2018… love Pete, Meagan, Bronx and Saint,” Wentz captioned his post.

The pair, who began dating in 2011, are already parents to son Saint Lazslo, 3; and Wentz shares son Bronx Mowgli, 9, with ex-wife Ashlee Simpson Ross.

Over the years, the Illinois native has enjoyed blending his rock star lifestyle with his young family.

“There are cribs backstage!” Wentz told PEOPLE in 2015. “My family’s pretty nomadic. We’re able to move around, and that’s the only life that my kids have grown up with, so I think it’s somewhat normal. It’s pretty fun.”

He added, “There’s nothing like a bus to put a kid to sleep: It’s really dark, and the engine’s really loud.”

The rocker — whose new album with Fall Out Boy, Mania, drops Jan. 19 — has been on the road with the band promoting the LP and will continue touring in 2018.

“In order for us to have kept doing the band, we needed to grow up a little,” Wentz previously told PEOPLE of getting the band back together after a hiatus. “I think we’ve done a pretty good job with it so far.”