I don't want to give my brother any birthday or Christmas presents.
Why don't you want to give your brother any birthday or Christmas presents?
Because he can buy anything anyway. I think it's a waste of money.
I understand why you feel that way, but gifts aren't about the money. They're to show how much you care about the recipient. You don't need to spend a lot on gifts for your brother, just make sure they're special.
Wtf, so now I'm obligated to give him presents simply because I'm his brother.
You aren't obligated to give him gifts, but it's nice to give family members on Christmas and their birthdays. I'm sure he would appreciate getting something from you, just like most people enjoy getting gifts.