WARREN BEATTY has finally accepted his transgender son – and to prove it he celebrated with a family “coming out” party in Hollywood just a week before Christmas!

The “Bugsy” star and his actress wife Annette Bening smiled for photogra­phers when they went out with their four children – including 19-year-old son Stephen Ira Beatty, who was born a girl and named Kathlyn – at il Covo Italian restaurant on Dec. 17.

“While Annette has always ac­cepted Stephen’s transition, Warren struggled with it,” an insider told The ENQUIRER. “Warren never stopped loving their child, but he had plenty of issues and fears to overcome.

“The bottom line is he missed his little girl. But he’s finally resigned himself to the fact that one day Stephen will probably have gender-reassignment surgery and legally become a boy.

“Warren still slips up and calls Stephen ‘her’ or by his birth name Kathlyn. But the bottom line is he’s totally onboard with his child’s new lifestyle.

“The dinner was an unofficial public display that he’s proud of his family, especially Stephen, for having the courage to be who he truly is.”

EXCLUSIVE pictures and ALL the details are only in the new ENQUIRER- on sale now!