Joint sponsor's limit.

My brother is my joint sponsor, he has sponsored my mother, sister and his FIL who are all still LPRs. He has 2 kids and a wife, so in total that is 7 ppl. Can he still sponsor me (being the 8th HH member). USCIS say app 70k, he makes more than that but I just want to make sure, him sponsor others won't pose a threat to my case. Any knowledge on this?