I have namechanged for this so as not to out myself or anyone else!
I will try to keep the backstory brief to avoid drip feeding. My brother has been married for about 8 years to a woman who always seemed pleasant enough but had some red flags - absolutely no friends; very insular life, etc. We (by whom I mean my dad, other brother and I) liked her well enough, but she never really had all that much to say for herself, so I can't say we knew her very well in hindsight at least.
Initially she got on well with my dad in particular, and he paid for lots of meals out, holidays etc, and ultimately for her wedding. A few years after getting married, they had a little boy, and at that point, her behaviour changed totally. She became very angry with my brother and controlling of the child - for example, you'd go round there, and you were never allowed to pick up the baby or to read to him or feed him. You were allowed to look, but not to touch. She was also incredibly critical of my dad and how he interacted with the baby. My dad is a great granddad in my view; his other grandchildren love him to bits, but SIL thought he was too loud and rough and put him down constantly.
After a year or so there was an incident with my SIL and my dad. I won't go into detail as it could out me, but suffice it to say that to the extent my dad was in the wrong, he was at worst insensitive, and would have been mortified to think he had caused any upset/offence. Certainly had he been told what he had done, he would have apologised. But instead SIL acted like it was the worst thing in the world, sent a truly disgusting email that was dripping with malice and venom, and put a ban on my DN seeing any of the family. If my brother wanted to see his family, she would make up some transparent excuse (it's amazing how often one perfectly healthy woman can hurt her back!) to stop it.
At birthdays and Christmas, we were told that we could not see DN, but presents would be taken off us a few days in advance so that DN could open them with SIL's family. I like to make a big deal out of presents; I am lucky enough to have disposable income and I like to spend it on people - but I do like to watch the recipient opening them! So I refused to do this, and told my brother that I would go shopping with him and DN to choose things. In response I got an email from SIL saying that DN was too young to go shopping with "a stranger", but she would tell me what I could buy and post to them...
About a year after this, I got pregnant. This did not go down well with SIL, who said some breathtakingly horrible things about me, the baby and my partner (whom she's never even met) to some very old friends of mine, putting them in a very unpleasant position. She also sent a few more unpleasant emails to my dad - amongst other things throwing my dead mother (whom she also never met) in his face. None of us have been in touch with her due to not wanting to make my brother's life any worse, so she never got any reply to any of her rants.
Shortly after that, SIL got pregnant herself, and had another boy. He's now about 18 months and we've never seen him, and haven't seen his older brother since he was a baby.
Until now, I've maintained the stance that I will buy them anything they like so long as I can see them and they know their aunt. But it's getting to the stage where my brother is buying nice presents for my baby, and I feel guilty that I am not reciprocating. On the other hand, I don't see why I should buy presents for children who have no idea who I am, and who are going to be told a pack of lies about me and my family as soon as they are old enough to ask!
It's clear that my brother should stand up to his wife, as he's the one who's missing out on so much, but he's not, and that's his business, not mine. But AIBU not to buy them Christmas presents this year in light of the fact that my baby always gets nice things from him? WWYD?
Sorry for the epic!