Ryan Reynolds knew Blake Lively was the one for him after one very good dance.In GQ Men of The Year issue, Reynolds proves why he's one of half of Hollywood's best couples by sharing the exact moment he knew Lively was endgame.It started with a date at a restaurant in Tribeca, which was open "super late" and nearly empty."This song came on," Reynolds recalled, "and I was just like, 'Want to dance?' No one was in there, so it was just totally empty. And it was just one of those moments where halfway through the dance, it was like, 'Oh, I think I just crossed a line.'" It was a good line to cross, one that ended with him walking her home. "And, uh, you know," Reynolds said, "I don't really need to go into what happened after that."We already know a true gentleman never kisses and tells, but Reynolds is the kind of guy who doesn't dance and tell. When asked about the song that they danced to that night, Reynolds stayed mum. "I do," he said, "but I'm not gonna say. You're shut out."Whatever song it was, it was clearly a good one since Reynolds and Lively are now married with two children and more adorable than ever.Need more proof? Check out these photos of the couple from Reynolds's recent 40th birthday. Yeah, that's love.