Ok, I've done some more reading and it seems like what we should do is for my husband to file I-864 for a household of 2 (or 3, including our child, me and him?) and my mother-in-law filing her own I-864 for a household of 4 (her, her husband, their child and me). What if her income does not meet the requirement for 4? Her husband works but we would not like to include his income in the application, if possible. help! thanks!