Pete Wentz has become a father again.

The Fall Out Boy musician and his girlfriend Meagan Camper, 29, welcomed their second child - a baby girl - called Marvel into the world over the weekend.

Taking to his Instagram account on Sunday (13.05.18) night, the 38-year-old rocker uploaded a photograph of him, Meagan, their new baby girl, their three-year-old son Saint and Pete's other son Bronx, nine, from his relationship with Ashlee Simpson.

He captioned the sweet shot: ''So excited to introduce Marvel Jane Wentz. Feeling so grateful that she's here... annnnd she's already ready to takeover the world happy Mother's Day @meagancamper and all the moms out there. We [love] you. (sic)''

The pair announced they were expecting another little one at the beginning of the year when Pete posted a picture of his two sons holding a pink present and wrote: ''Happy New Year! We're kicking the year off with news of the best gift yet: [baby girl emoji] coming to our family in 2018... love Pete, Meagan, Bronx and Saint. (sic)''

Meanwhile, the 'Centuries' hitmaker previously likened being a father to taking ''happy pills'', as he finds his young tots' laugh to be ''the funniest thing on the planet''.

He said: ''I have two kids, and if I hang out with them it's pretty much like taking happy pills. When you hear a one-year-old laugh, it's pretty much the funniest thing on the planet. It changes my mood ... My highs, my happiness are really high and my lows are very low and I'm not able to regulate between the two. Through actual therapy and having kids it's way more under control and something I can see when I'm on the roller coaster and control it more.''

He also said he'd like to make sure the world was a happier place for his brood.

He said: ''I think that I look out at the world sometimes, especially having kids, and all I see is negativity and hate that's so divisive.

''It bums me out and I know that people have a hard time - I've had a hard time - and one of the things you should know if that you can make it out of the other side and be stronger because of that. That's why I think it's important.''