Warren Beatty's teenage daughter with Annette Bening wants to undergo sex change surgery to become a male, according to a U.S. tabloid report. The National Enquirer claims 18-year-old Kathlyn Elizabeth Beatty, the Hollywood couple's eldest child, has adopted the name Stephen Ira and has been dressing and living as a male for some time. The teen, who is now legally allowed to make her own medical decisions, is said to have been researching the gender reassignment operation - the same surgery Cher's daughter Chastity underwent earlier this year (10) to become Chaz Bono - with a view to having the procedure done in the coming months. A source tells the tabloid, "She repeatedly told her parents that 'once I turn 18', she would take matters into her own hands. "Warren knows he can't stop her from following her dream... He and Annette have tried to deal with this over the years when their daughter was younger, but she's determined to go ahead with a transgender operation, just like Chastity." Representatives for both Beatty and Bening have failed to respond to requests for a comment, but - 's photos of Kathlyn from last summer (09) appear to back up the claims. We snapped the then-17 year old at LAX airport with her mum, but her short, boyish haircut and her masculine dress sense had us mistaken that it was her brother, Ben, in the photos! Annette Bening and her daughter Kathlyn Elizabeth Beatty arrive at LAX to catch a flight to Boston Los Angeles, California.