From this article:
http://espn.go.com/espnw/more-sports/7116870/alex-maia-shibutani-make-ice-dancing-family-business
So it sounds like Dad is unlikely a Japanese citizen (or likely gave up dual citizenship long ago), so it would be through their mother.
Anyway, these posts are laughable. For me, the fact that people see this result as the Shibs regressing and/or a federation dumping is actually an insult to the improvements made by the teams behind them. The Shibs had a very strong FD and the fact that Chock and Bates beat them, speaks to the fact that Chock and Bates have improved greatly. Not to mention the fact if they didn't have a deduction for an extended lift, they would be virtually tied.
I'll note that the Shibs beat C&B in PCS in both segments.
And yes golden, I agree with you -- they clearly love skating with each other and for team USA and they have a connection with each other that they can't replicate with other partners.