Sorry for the length but I really don't know what to do for the best. DH and I are married with 2 DC - DD13 and DS9. My parents are both dead, have been for several years.
DH's father is estranged so we only have his mum as a close relative. DH also has a DD from a previous relatio nship who is 31. All was good and MiL helped out with childcare when DC were tiny etc. Then it all went wrong xmas 2019.
MiL is strongly anti-tech. Has a basic mobile for emergencies but that's it. Internet is evil and gaming is literally the work of the devil. Never mind, that;s OK her choice. For xmas 2019 DS got a Nintendo Switch. We have been very strict with him and on Xmas Day he was allowed 1 hour on it so he took part in Xmas (we have xmas day at ours with MiL staying over), with the promise that Boxing Day he could play on it properly, set it up etc. This is a child that trains with academy level football 5 to 6 days a week after school and is very sporty. Allowing him a break over xmas was fine with me and DH.
DSD came over on Boxing Day to spend time with MiL and us and then drove MiL home. MiL then told us by text that DSD had been very upset that DS has ignored her playing on the switch and I was playing harry potter trivial persuit with DD. DH called DSD (ie his DD) and she was baffled and said all was fine, she'd had a nice time etc.
Things remained frosty through January and we didn't know why, then covid hit and MiL had to shield. Over 2020 DH's brother and his wife, who live nearer to MiL and who both work p/t were happy to make sure MiL was OK with food etc. DH cooked some meals for the freezer and popped down occasionally to see her. He also took DC down to sit in the boot of the car and chat to MiL through her window. Things slightly thawed.
Then, just before xmas 2020 DS class bubble went down and he had to self isolate. Fairly standard procedure, DS was perfectly well. MiL gets it into her head (possibly due to sis in law whispering in her ear) that either 1. we were planning to bring DS round to see her and 'infect her' or 2. DS was going to get very ill and we wouldn;t tell her if he went into hospital. Neither of which was true or would have happened. Sis in law also seems to dislike me and I don';t know why.
Bottom line was MiL then texts DH calling me the most horrible names and that I ama complete bitch controlling him. At no point have I ever contacted her and wound her up so we have no idea where this has come from. She then texts saying DH is dead to her. On his birthday he doesn't even get a card. DC are upset at not seeing their only grandparent.
Fast forward to now and after not hearing from sis in law for the whole year, we find out that over the past couple of weeks MiL has deteriorated in terms of personality. She has started to refuse to see anyone except DH's brother and occasionally his wife. The brother has had to move in with MiL as she is not functioning and forgetting to eat. She has piles the size of golf balls. They took her into hospital yesterday and all her bloods have come back as free from infection and she's having an MRI scan today. We initially thought she could have a bladder infection but now I suspect dementia. She is 77.
I just don't know what to do. It seems DH's brother and sis in law only told us after DSD told them they must. What do I do about the DC? They've not really properly seen their nan for almost 2 years and I am simply so sad for them. They adored nan. She's their only grandparent that they know. If ypou've read this far thank you. Neither of my parents made it to old age so I'm out of my experience zone. How do I help, how to I help my kids and DH?