Pete Wentz and Ashlee Simpson shocked the masses when they split.
Taking things a step further, the once-amicable divorce process is turning ugly. Pete does NOT want his soon-to-be-ex to have primary custody of son Bronx.
He's now taking her to court as a result. Wentz just filed legal papers in response to Ashlee's divorce petition ... asking the judge for JOINT custody.
Ashlee had checked the box that indicated she wanted primary physical custody of Bronx Mowgli, 2, who was born shortly after the couple got married.
Wentz also wants each party to pay their own legal fees, even though Ashlee had asked the court to make Pete foot the bill for both parties.
Ashlee didn't specify the official break-up date, but Pete says the two called it quits February 9, right after Pete's wife-less Super Bowl Trip.
Pete's constant touring is believed to be the reason for the breakup.