The 20-year-old Jonas Brothers singer - who has previously romanced teen stars Taylor Swift, Camilla Belle and Demi Lovato - and the 'Twilight' actress have been spotted on numerous dates since July and now pals say the romance is heating up.
A friend told Life and Style magazine: "When they're not travelling, they're basically living together."
Joe and his brothers Nick and Kevin - who married his long-term love Danielle Deleasa last December - hit the headlines for wearing 'purity rings' to represent their vow to wait until marriage to have sex. However recent sightings of Joe without his ring have led to speculation that his relationship with Ashley is serious.
The pair were recently spotted enjoying an intimate dinner at The Ivy restaurant in London and attending a Kings Of Leon concert together.
As well as meeting up in London - when Ashley was promoting 'The Twilight Saga: Eclipse' and Joe was supporting brother Nick, who was making his West End debut in 'Les Miserables' - the duo were also spotted having dinner together at The Alcove in California at the end of July, with the singer seen getting the actress' bag from his car.