This is mainly for my DH, but also for me. Complicated, so I will try and sum it up, bear with me if it is a bit long !
Fil had a (diagnosed) personality disorder, and was a total nightmare to deal with, narcissism, manipulation, abusive behaviour. He is dead, but Sil is very similar to him, although more functional, she has a child and at the moment is managing well, although in the past she has been hospitalised. She is very deceitful, has a massive ego, and an inflated sense of her own abilities and importance. We don’t know if she has been given a diagnosis of a pd, but she fits the pic for a narcissist.
Mil shores this up by praising everything Sil does, and refusing to support DH , even when Sil (who is pathologically jealous of DH and competitive, and will lie etc to manipulate things to get her own way) has behaved terribly.
Dh has gone minimal contact with his sister. He does have contact with his Mum, but it is upsetting and difficult, as she favours SIl over him all the time. Small things that have mounted up, eg she will go to Sil’s dc’s party but not our dc, allows Sil’s DH to treat my DH badly etc.
He loves his Mum, and I also do care about her but have found her increasingly hard to deal with, maybe I have just reached my limit, I don’t know. However she is my dc’s only Grandparent, so I make an effort partly for their sakes, partly for DH. She has done the odd thing for dd1, paid for a school trip away, that kind if thing, but she does nothing else for our dc .
Mil is in her eighties, and worryingly, sounds more and more like Sil when we see her. She parrots things that Sil has said, and seems almost manipulated by Sil into decisions that also affect us because
there is a family business that they are all part of, and that is a huge part of the problem , as DH has to still negotiate with Sil and work with her at times, ditto his Mum.
DH is a very honest and straightforward person, but the more he is straightforward with his Mum, the more she seems to resent him. He has tried to talk in a calm way about how she treats him and Sil so differently, but she just gets annoyed. ( is impossible to talk to his sister at all , so he only speaks to her in a formal setting, at meetings, and avoids any other interaction).
Any advice on talking to Mil without making things worse, and on dealing with a narc in a family business setting ? DH is the least Machiavellian person imaginable, but I think he needs tactics ! Sil will absolutely do anything she can do undermine and damage DH, and she now seems to have an enormous influence on MIl, which means she could potentially have an influence on decisions which could have financial ramifications for us.
So two main issues , managing a narcissist without getting shafted by them, and talking to a parent who seems to have swapped one domineering narc (fil) for another (sil). Weirdly DH very much seemed her favourite when he was much younger, but she is not happy that we kept our dds away from Fil, and blames me in particular for this, even though Fil was abusive to me .