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Pete Wentz and girlfriend Meagan Camper are spending more and more time parenting Pete's son Bronx, as his ex-wife Ashlee Simpson is busy traveling and partying with friends ... according to a new report.

The "Pieces of Me" singer has let her Fall Out Boy ex take primary custody of their 4-1/2-year-old son so she can live her life freely and Pete's not too happy about it, according to RadarOnline.

"Pete’s told Ashlee that enough is enough, and she has to cut back on the partying. He’s even spoken to [her mom] Tina to get her take on the matter and make sure that he’s not overreacting in any way. She reassured him that he isn’t and said she’s been worried about Ashlee too," according to the website's source.

You think Pete and Meagan are headed to the altar? And will they take primary custody of Bronx?