The singer-and-actress and her Fall Out Boy star husband have put their $4.5 million home in Beverley Hills, California, on the market after deciding it wasn't "kid friendly" enough for their son Bronx.
A source told Life and Style magazine: "The house is built into the side of a giant hill and it doesn't really have any yard.
"Now that Bronx is getting older they realised that really isn't a child-friendly house."
"They are going to sell this house and look for something that will be better suited to young children."
The four-bedroom house is built over four floors with swimming pool, gym, media room, gourmet kitchen and a master bedroom with his-and-her baths.
The couple, who married in March 2008, bought the mansion in January 2007, but need more space for 10-month-old Bronx Mowgli and his planned siblings.
Speaking about his wish to expand his brood, Pete, 30, said: "Everything is awesome about being a dad. Eventually we want to be able to have our own soccer team!"
The couple - who put baby plans on hold while Ashlee, 25, was shooting 'Melrose Place' - may now start trying for a baby following news last week that Ashlee has been dropped from the show.
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