Clarification on Sponsorship

[YayaYiyi 0]

A. I don't have a birth certificate for my grandfather who is willing to sign a I-864A so that I can list his income. Will not having this bar him from being allowed? I did not read anywhere where this was necessary on the forms for an I864a.

B. My mother will joint sponsor. There is a check box that asks if she is the only joint sponsor. Would my grandfather who signed an I-864A be considered a joint sponsor? Or would my mom still be the only joint sponsor if he was accepted?

Also, I plan on sending the paper work for whichever scenario they want to classify us as. Meaning, I will submit paperwork for my grandfather with an I-864a w/out birth certificate and then tell them that if that is not sufficient, then use mom as the joint sponsor.

And, I am confused about when the joint sponsor paperwork is asked for. If I send it in with my I864 at the same time, knowing I will need a joint sponsor, will they process it then? Or, I have read where they ask for this documents from my wife in the Philippines to bring to the interview? If that is the case, then there would be no sense in sending in the I-864 of my mothers at this time.