Taylor Swift Calvin Harris Is ... In with Mom

12/15/2015 10:23 AM PST

Taylor Swift: Calvin's in with Mom

Just when everyone thought Taylor Swift and Calvin Harris might be on the rocks, he reappeared in a big way ... by getting some face time with her mom.

Tay-Tay celebrated her 26th birthday with her parents at a friend's house in Bev Hills, and Calvin made the cut for the dinner party. The couple hadn't been photographed together in some time ... so, of course, the rumors started flying. 

Calvin knows the old rule even applies to Taylor -- charming Mom paves the road to banging charming the daughter.