"Mum and baby are healthy and happy," a rep for the Fall Out Boy bassist told People. "They are thrilled at the addition to the family and Bronx is over the moon to be a big brother."
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Pete Wentz and his girlfriend Meagan Camper have welcomed son Saint Lazlo
Bronx Mowgli is Pete's five-year-old son with his ex-wife Ashlee Simpson – Ashlee is now engaged to Evan Ross.
Pete, 35, and Meagan, 25, announced that they were expecting a baby together in February with an adorable Instagram snap.
"We're super excited to announce we're expecting a baby," the musician captioned the photo of them cuddled up in bed.
The couple announced they were expecting a baby with this sweet snap
It is thought they chose not to find out the child's gender ahead of the birth.
"What's more exciting than having the pitter-patter of another little gremlin running around?" Pete said back in May. "Now it will be two-on-two."
Pete and Meagan have been dating for around three years now – and have made no secret of their plans to start a family together.
Pete Wentz recently shared this photo of Meagan as they awaited their baby's arrival
"They've been planning this for a while," a source close to the couple told People.