Adjustment of Status - I-485

I just received the mail of rfe that said I didn’t fill out the I 130a form and I didn’t know guys if I was supposed to fill it at the first place or not , if anyone has the same thing in their request for evidence or not ?
secondly, It said my joint sponsor has to file I864a contract with his household ( which is his wife ) besides the I 864 that he filled before to meet the lowest income requirements of being a joint sponsor .
my question is if he didnt meet the lowest income requirement by himself at the first place , would he be able to sponsor me with his household together or what do they mean by missing out filling I 864a form as a contract proving that they can both meet the requirements even though they’re separate family than me and my wife . and thank you in advance