Bahamut is a dragon of Meracydia, and a primal... I don't think it's related to Midgardsormr. Can you link your source?

Also, even if I know that there were those dragons in FFXI (Jormungand, Tiamat, etc...) I think they will follow the Norse folklore trail, so no Ouryu (clearly a japanese name) and maybe no Jormungand (it's a different name for Midgardsormr, in the mythology... but they could ignore this, of course ^^).