I can see the terrible situation you are in.
How long has this been going on for, when did they first decide to split? Who wanted the split?
I know when I first instigated my divorce, my stbxh was very, very cross that I would be due 50/50 (very long marriage). He said a lot of things about what he was going to do, what he wanted, what he thought was fair (it wasn’t).
I was the one who used a solicitor from the get go. His demands got more reasonable once he’d seen a solicitor. Solicitors are very good at telling you the hard truth and making you see sense. Eventually things have to be signed off by a judge and they won’t sanction anything that seems too one sided.
You say your DB initially didn’t want her to have anything, she may still think that this is his attitude and she is just behaving in self protection. You say he has sent letters and she hasn’t replied. Do you know if she has even opened them?
So you (your DB), needs to find a way to break this impasse.
I think the most likely outcome will be the house needs to be sold and the profit is 50/50. Does your brother accept that his deposit is likely to be split as well? They were obviously together awhile before he bought the house.
If so, he needs to make sure his wife knows this. They probably need to do a reset in their hostility and suspicion of each other.
How to break the impasse? A letter or email, suggesting the above, a mutual friend to pass on the information, a meeting in a neutral place, with or without a neutral friend?
Perhaps she needs that talk with the solicitor? Sometimes you can get a free consult with a solicitor. If she won’t pay to see a solicitor, would someone else stump up the £250 so she can have an hour with one?
This may be enough to make her realise there is just not enough money for her to live there for the next 13 years.
It may be the best £250 your family has ever spent if it gets you to the next step.
My ex bombarded me with texts, letters and emails telling me how outrageous it was for me to have 50%. It was only once he’d calmed down and knew what the legal situation really was that we have been able to progress. Him getting a new live-in girlfriend has also helped.
My ex actually sent me an email and he wasn’t being ironic that if we split everything 50/50 - he wrote “you will be living a life of luxury, while I will be in penury”. What he meant was he wouldn’t be able to live his life of extravagance anymore, and I wouldnt have to continue living so frugally.
If your DB was anything like my ex, he may need to backtrack a bit, and his wife needs to know his views have changed.
If this is not the case then the wife is trying it on.