Blake Lively and Ryan Reynolds
Sam Sharma/Pacific Coast News
10/22/2011 AT 06:30 PM EDT
Happy birthday to Ryan Reynolds
The actor, who turns 35 on Sunday, is celebrating this weekend with someone special: Blake Lively
The Green Lantern
costars – and their dogs – were spotted Saturday morning outside an apartment in Boston, where he's filming the action film, R.I.P.D.
And this is no casual birthday meet-up. "They are very much a couple," a source tells PEOPLE. "They're really happy together."
Lively, 24, recently split
from Leonardo DiCaprio
after a summer romance
, and Reynolds is still friendly
with his ex, Scarlett Johansson