Ashlee Simpson-Pete Wentz divorce shocker

This is one celebrity split we really didn’t see coming: the seemingly happy Ashlee Simpson and Pete Wentz.

Simpson, 26, filed for divorce from Wentz, 31, in Los Angeles this week, citing irreconcilable differences. According to documents obtained by TMZ.com, Simpson is seeking sole physical custody of the couple’s 2-year-old son, Bronx; however, Wentz is asking for joint custody. Simpson is also asking for spousal and child support.

The two got married in 2008 after dating for about two years. According to reports, a prenuptial agreement was not signed.

Sources said there was no third party involved in the split, and that Simpson and Wentz simply grew apart — due in part to Wentz’s hectic work schedule.

“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.” a source told TMZ.

The couple released a join statement yesterday that said: “After careful consideration, we have made the difficult decision to file for divorce. We remain friends and deeply committed and loving parents to our son, Bronx, whose happiness and well-being remains our No. 1 priority. We ask that everyone honor our privacy as we navigate this next phase of our lives.”

Meanwhile, Simpson’s older sister, Jessica Simpson, is engaged to former football player Eric Johnson. Johnson asked Simpson to marry him in November.