I didn't think CAB would be able to do much for you OP. But yeah, you and your brother both could do with speaking to (separate) solicitors.
I wish MN would make their mind up around these things.
Last week there was a post from someone who's children had inherited from Grandad (named in will) and her sister who didn't have children at the time and had stated that children weren't on her agenda, had a child years later and wanted some of the inheritance.
There were a lot of posters advising the OP that she should remortgage, give her sister the money etc when the children were actually named, and not calling the sister grabby, yet this OP has been flamed for asking the question when her FIL knew that the child was due to be born.
In all fairness, there were just as many people wading in to support the OP on that thread, and dozens pointed out that executors have no right to vary the will to better reflect what they think is fairer. And MN has thousands and thousands of active posters. There's sometimes going to be divergence of opinion when different people talk about similar circumstances, because you're not always going to get the same individuals posting.
Also I think the OP is getting a bit singed here because of the comment that her child shouldn't suffer just because he's not in care. That was very ill-advised, and the OP in the thread the other week didn't come out with anything that thoughtless.