@Steven Blanton I am going to echo a lot of the previous thoughts. My comments are also on the presumption that I will not opine on your personal/familial situation (I don't know your family dynamics) and regardless of family or not, you must strip the emotion out of the deal.
Think about your question in basic Economics 101: What is the supply (capital partners) out in the marketplace for the demand of your deal?
If you have a great deal with tons of demand you can start dictating the terms and tell a lender/partner to pound sand because they are out of line from the other deals you have.
However, if the demand for your deals are low/non-existent because you're inexperienced (nothing wrong with that - we all started somewhere) and have little to no cash to put in the deal (again we all started somewhere) then you might need to take what you are given and start building from there.
If after a couple of deals you prove that you have a great skill-set of finding deals, operating them successfully, and hitting great numbers you can (in other words) tell your brother to get lost with those numbers he's offering. But first, you need to have demand for your deals and unfortunately in this game you almost need experience to be trusted, so this deal might be best through your brother (who let's not forget is seemingly taking ALL the risk).