I read the link you provided and Thank you very much. Now I am clear with question 2(Q2) .If I sponsored my father in this I-864, I should not mention my mother in 9a since I sponsored her in another I-864. I can put my mother in Part 5. Sponsor's household size item f even if she has not got GC yet. Thank you for your post.
But I am still confusing about whether I should also put my parents in law in Part 5. Sponsor's household size item f. I did not sponsor their GC application but my husband did 4 years ago, and I used my husband's income and my income together in either my father's or my mother's I-864 form this time. Please advise and thanks a lot.