Okay, I'm back. I checked out the Final Fantasy Wiki first and saw this on Vincent's page:
"Kazushige Nojima has noted Vincent is naturally a loner, and had he not been a former ally of Cloud and his friends, it is unlikely he would have joined them in the battle with Bahamut SIN in Final Fantasy VII: Advent Children. His voice actor, Shōgo Suzuki, noted Vincent's few appearances have a profound impact and that Tifa Lockhart's remark "they're our friends", after Vincent's arrival, shows his underlying warmth. He is noted to be similar to Cloud, only more mature, which influenced his character and voice work."