There is, of course, a complex back story, but I don't want to write a very long opening post, so I'll try to keep things concise.
DH and I have been married for 20 years, with 3 DC. His mother and sisters have been problematic throughout, overstepping boundaries, being manipulative, and emotionally abusive. MIL put me through an enormous amount of stress and anxiety when DC1 was born. She is childlike in her emotional maturity and uses the silent treatment (for weeks, months or years if necessary) to try and get her way.
A few years ago, FIL died. He was the peacekeeper and tried to reconcile family issues when he could—he was sent in as MIL's flying monkey numerous times. Two years ago, DH argued with MIL. The underlying theme of the row was that MIL often causes problems in our family by trying to create divisions amongst our children, making special occasions about her, or giving DH the silent treatment for long periods—just generally manipulative and petty behaviour.
After this particular argument, MIL, SILs, and DH's cousin have completely cut contact with us, save for Happy Birthday text messages to our children. They refuse to talk about it (I have tried with MIL and SILs) and there seems to be no end in sight.
DH tells me MIL will give him the silent treatment for years, and he thinks this is the end of their relationship. I am so angry with them. Not at first, but so much time has now passed, and they have missed almost a year and a half of the children's lives. They have caused so much damage - our children are hurt. They have been dropped by their grandmother and the rest of DH's family because MIL can't bring herself to try to repair things with DH. She won't even answer the phone to him. Our eldest child had a significant birthday last week, and MIL didn't acknowledge it other than a stupid text - Love you so much, Miss you! ... Then why have you cut them out of your life?!
For context, our children are the only grandchildren, and throughout their lives, MIL has maintained that they are the centre of her world.
I don't know what to do with my anger and confusion. How can our children be so hurt by their grandmother and aunts? I can't forgive them and want to tell them they have ruined everything. I think MIL is under the mistaken impression that she can waltz back into their lives once she feels she has sufficiently punished DH with the silent treatment.