:shocked: *touches shh! and gets frostbite*
anyway, you're right, we can't really know what went on from just one person's perspective. But I certainly can't see looking after a dying mom as a big sin, even if there would've been better ways to handle it.
the fact that you're DJing for free even though you don't seem to really want to be there (and I wouldn't blame you) suggests to me that you're either a completely selfless giver, or that you feel guilty.
but.. whatever her brother may think of you now and whether or not that is justified or not.. I hope he isn't stupid enough to mess up her wedding by causing drama. Try to ignore it if he's giving you the evil eye.