Very weird, very hurtful.
My mum gave DB a huge chunk of her savings as deposit to buy the house he and SIL were living in. He has never worked, SIL sends most of her money back to her family abroad. Both thought they were entitled to be kept by mum.
Anyway, she told a number of people in family, including 2 female cousins who repeatedly told her to tell me, but no, not a word. There was the odd time something slipped out, and I questioned her, but she covered up, denied etc. A couple of weeks before I found out (when she was ill and I started being involved in finances) my DB was talking about his landlord - the one he hadn't had for about 3 years!
I know mum was blackmailed by DB into keeping quiet. He's biggest shit stirrer on this planet (or was, cant now she no longer with us). He was also greedy, knew that if she wanted to give me same, it would reduce any eventual inheritance he might get. Oh and how he would have gloated when she died and I found the paperwork for money transfer, which she had kept. He loved gloating about him being favourite.
I was very very hurt, not about the money, we work and earn every penny we have, but about the obvious shutting me out and treating me different to him. The secrecy, telling others in family but swearing them to secrecy. Awful. When I found out, both cousins said how sorry they were, they wanted to tell me but darent.
I went NC for a short time but had to help look after mum as she was dying. But I lost all respect for her and did what I did in the last year to give me a clear conscience. DB and I are v v low contact now.
I suspect one of your DHs siblings stirring. Could they be jealous? My DB was, as he didn't have a house/decent life like I did, because he chose to sit on his backside all day rather than work!!!
I would go Low contact, and certainly wouldn't feel obliged to spend birthdays and xmas with them.
As pp said, you cant choose family. I do wonder why I got lumbered with mine, my DH family are so normal by comparison.