The Grey's Anatomy star - and BFFs with Kat Heigl - has split from his much younger boyfriend Mark Cornelsen, reports In Touch...

A pal explains that "it just came to a natural end, no hard feelings." Of course, T.R. is asking Mark to move out of the apartment they shared together.

So much for the past two years! Think their age difference of 16 years (T.R. is 36) had anything to do with it? I mean, Mark isn't even allowed to drink yet!