The deed should reflect reality. Since your brother is in fact your co-owner and is paying 50% of the costs, you definitely should add his name to the deed and pay the mortgage and taxes from a joint account. This is a much cleaner method than your paying 100% and cutting him a check. Adding his name to the deed will let him deduct the 50% of the property taxes and mortgage interest that he's paying, and also lead to a 50/50 split of the capital gain (if any) when the house is sold. Doing so will also help avoid future legal/tax complications, for example if one of you should die.
**Answers are correct to the best of my ability but do not constitute tax or legal advice.
