"After careful consideration, we have made the difficult decision to file for divorce," the couple said through a spokesperson. "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."
According to TMZ, the divorce documents were filed in L.A. Superior Court, with Simpson, 26, citing "irreconcilable differences" and seeking spousal support.
In the court papers, which were signed by Simpson-Wentz on Monday and filed on Tuesday, it says the couple's date of separation is to be determined. Simpson-Wentz is seeking primary physical custody of their 2-year-old son, Bronx, with visitation for Wentz. She is also seeking to go back to her maiden name of Simpson and drop "Wentz."
Simpson, a singer-actress and the younger sister of Jessica Simpson, and Wentz, the former Fall Out Boy bassist, 31, married in May 2008, and by that November welcomed their child, Bronx Mowgli Wentz.
The couple had been linked since the fall of 2006, when they were spotted kissing at a New York nightclub. They announced their engagement in April 2008, and their wedding was officiated by Simpson's father, Joe Simpson.
Only last week, Wentz was sharing his and Ashlee's Super Bowl recipes with PEOPLE.