The way they talked to each other in the "Making of" didn't give me the impression that they were related in any way. He's been with the dancers for a while now and seems comfortable with Ayumi, though. He was also in the "fairyland" PV as one of the dancers.

I still can't believe people ask this question, he wears an open vest in the PV and you can see his chest, which is clearly a man's chest.