The amicable split between Pete Wentz and soon-to-be ex-wife Ashlee Simpson-Wentz appears to be taking a slightly less friendly turn. The couple, who separated earlier this year and seemed to be on good terms, appear to be headed to court to resolve a brewing custody dispute over their 2-year-old son, Bronx.

According to TMZ, Wentz filed papers on Monday in response to Simpson’s divorce petition. The former Fall Out Boy bassist asked that a judge grant joint physical and legal custody of their son and requested that each spouse pay their own legal fees. The gossip site also claimed to have obtained a copy of the divorce petition, in which lawyers for Simpson-Wentz checked a box indicating that she wanted primary physical custody of the toddler and that she wanted Wentz to pay her legal fees as well.

The Wentz form lists May 16, 2008, as the date of their marriage and February 9, 2011, as the date of their separation.

When news of the divorce broke last month, sources close to the couple said they were intent on riding out the split peacefully and putting their focus on Bronx’s well-being. “It’s very amicable. They’re on very friendly terms and speaking — it’s fine,” an insider told People magazine at the time. “They’ve just grown apart. They’ve been growing apart for quite some time.”

The source added that parenting their toddler remained their top priority. “It’s all about Bronx for them. They’re fantastic parents — Pete says she’s a great mom, and she says he’s a great father,” the insider said. “It’s about Bronx’s care and well-being and happiness for them.”

Insiders have also echoed the “growing apart” reasoning to TMZ, adding that their respective careers — Simpson has largely eschewed the spotlight since 2008′s Bittersweet World, while Wentz has dabbled in fashion and piloted other musical projects — wedged them apart.

“After Bronx was born, Ashlee made a conscious decision to get out of the business, but Pete’s heart was in music so he kept touring and that became a big issue in their relationship,” the source added.

While insiders have maintained the split is drama-free, TMZ reports that Simpson left because of Wentz’s antics. “It’s really all about Pete’s erratic behavior,” the source said. “She really wanted out.”

Source: MTV.com