Once Upon A Time co-stars Jennifer Morrison and Sebastian Stan have quietly ended their romance.

The couple started dating last year (12), but split four months ago, according to UsMagazine.com.

A source says, "They have gone their separate ways - no bad blood... They just grew apart."

Morrison was previously engaged to her House co-star Jesse Spencer from 2006 to 2007, while Stan was once linked to Glee's Dianna Agron.