回复：His medical treatment failed in China, and he can't

It seems to be a good reason for I612 approval. But in this special case, do you think he will be in good condition one year from now, or even longer (given your I-485 might get rejected before J1 waiver approval) about the time of your interview, or you need to start looking for substitute sponsor (not a joint sponsor).

http://www.uscis.gov/portal/site/uscis/menuitem.5af9bb95919f35e66f614176543f6d1a/?vgnextoid=6a096c854523d010VgnVCM10000048f3d6a1RCRD&vgnextchannel=4f719c7755cb9010VgnVCM10000045f3d6a1RCRD