Hi
@Jake's Nan , If you think that long term a move nearer the family will be useful I would suggest you discuss this with him now. He will hopefully have more insight now and should adjust to a move easier in the early stages and would cope better with a move physically now. He hopefully will also be able to take part in discussions about what is suitable and what his long term needs may be.
By the time SIL thought we should move MIL to a smaller place it was very obvious that she would not be able to find her way around a new home or area so she has had to stay put. You also need to think about how much you or other family members are able to help. Moving house is a big thing - SIL expected us to sort it out as she lives in USA, but by then I knew that I was not willing to take on the stress of selling MIL's house , finding a suitable new house for her and organising the physical move all whilst also looking after her.
Please talk to your brother about Power of Attorney if you have not yet - if you wait until they are needed it may be too late. You need both the health and finance ones. You can do them online through the gov.uk website and they should be registered straight away so his attorneys can act under his instructions as things start to get more difficult for him. Think about who is best to be attorneys - if all the attorneys are older than him they may find the responsibilities too much as they get older.
In the early days MIL still knew what needed doing but could not cope with all the options when phoning utilities etc. When we got POA it was so much easier - I could carry out her requests without having to be physically present in her house (without it she had to give permission each time over the phone for me to act on her behalf).