My brother begs me to go and buy him stuff from the shop


So basically I would go up to the shop and my brother would walk in and say “you going to the shop...get me....(insert item) and I would be like “no” because it’s my money and I’m not spending it on him

And if I don’t buy him stuff he won’t let me go out (Btw he’s 26 and I’m 17) also he will beg me to go even when I don’t want to go, I know it seems a bit like a rant but I have no clue what to do