why? I assuming that the family member who is "hosting" wants to do it? They know or have some indication of how much it cost right?
Like I said I just don't believe in giving gifts (dinners etc) with strings attached. If you can't afford or are going to kevitch about the cost and the fact that guest aren't bringing stuff, then don't host.
Actually, the assumption that the person is hosting because they want to, is a broad assumption. In the OP's case, it sounds like her family includes herself, one brother, and her parents. Since her brother sounds very clueless, he is probably never going to take it upon himself to host. That leaves the OP, or her parents to host. I don't know her (OP), but in the past 10 yrs, I've tried to take some of the Christmas hosting off of my Mom. She deserves a break.
I have 2 siblings who never host anything, so are very oblivious to the work/cost involved. I have finally just started asking them to bring a bottle of wine, or some beer, juice boxes, etc. I'm happier and no longer resentful.