Hi Meth and welcome,
Although it is true, that the belief system of the (b)org often does tear families apart, to be fair and have a balanced view we can't always point a finger at them and say they were the problem. Many families today are dysfunctional, within the (b)org and outside the (b)org.
Some, like my immediate family for instance put the "family" first above the (b)org, even tho we are not what you would call a close family, blood still takes priority. I am not active and haven't been for quite a while now, however my father and mother have never abandoned me. I am not dissed, but it was made quite clear to me that even if I was it would have made no difference to them, or my sibblings. There are fanatics in every cult/religion call it what you want. However this is not always the case. Some in the (b)org have permitted themselves to become so consumed by the GB's ideologies that they are prepared to leave family, but I want to ask you this, and ask yourself this too, How close to each other was your family to begin with? (rhetorical question)
These days mothers and fathers abandon their children and families, and children abandon their parents, willy nilly without even so much as a second thought. So is it absolutely because you were all once in "The Troof"? I have read many testimonies on this and other forums, and many like yourself believe outright it was the (b)orgs fault, and maybe it was, but for some it just isn't entirely the case. I know many ex JW's personally that have left the (b)org, and their families have never abandoned them. So take courage Meth, maybe in time if your brother and mother re-evaluate family, they may just come to their senses.
Stay well.