The pair, who have two-year-old son Bronx, announced their plans to divorce earlier this month and Ashlee has turned to Jessica and her fiancé Eric Johnson for support.
A source told In Touch, 'Leaving Pete was tough for Ashlee and she needed to be with her family.
'Jessica told her she and [two-year-old son] Bronx were welcome to stay with them until she was ready to find a place of her own.
'There have been a lot of family dinners and lots of praying. Ashlee couldn't have asked for better support.'