yes me and my husband are the sponsors. So I am assuming I have to put 4 there? (me, my husband and my parents)?Assuming you are the sponsor, it's not "who depends on you" but "who is included in THIS application".
e.g. your children depends on you but they are not in this PGP application. You (and maybe your spouse) are in this application as sponsor, and perhaps your siblings are in this application as dependants to your parents.