Ashlee Simpson celebrates fiance Evan Ross' birthday with his mother Diana Ross

NEW YORK, Aug. 27 (UPI) -- Ashlee Simpson celebrated her fiancé Evan Ross' birthday on Tuesday with a bowling/dinner party.

The singer and Ross, who turned 26 Tuesday, were spotted hand-in-hand as they strolled outside Bowlmor Chelsea Piers in New York. Later that day the pair was joined by Ross' mother Diana Ross for dinner at STK Downtown.

Insiders claim everyone was "in great spirits" during the celebration and that there was "lots of wedding chatter at the event."

Simpson, 29, and Ross became engaged in January and will tie the knot over Labor Day weekend. The actor and musician reminisced over his special day on Instagram writing it had been "such a happy birthday" along with a selfie.

"It's such a happy birthday. I'm 26. On august 26," he wrote. "My golden year. And I will be married in less then a week. I'm feeling very thankful."