Sunblue - I went through the very same thing - I lost my Dad who was a great guy and left me with an NMother. Just last week I was thinking that his only mistake was marrying her. Anyway, my brother also abandoned me, two Christmases ago, I called him to ask what he, his wife and three boys wanted for Xmas. He said he thought that it would be easier to not exchange gifts. Easier? For who? I buy five gifts he buys one. Really? The last connection I had to him was our gift exchange at Xmas.
Brother moved on and entirely invested himself in his new family and her parents. Her parents gave them their house and moved into condo. A story for another day is that my brother loves hand-me-downs. Dont know how exactly this happened except NMom treated him badly, like a second class citizen, I think its an unconscious feeling he got from her. He doesn't work very hard towards financial goals, because in our house hard work was never rewarded so he underperforms and enjoys whatever crumbs he can get. He sure loevs used furniture, cars, clothes and other assorted used items he picks up at thrift stores and elsewhere. Very weird because Dad was wealthy, financial hardship did not exist in our childhood, but mother was a scrooge, withholding both money and approval.
My specific issue with him is that he went to marriage counseling in 1998 and discovered my Mom was N and NEVER told me. It took me another 10 years for me to figure that out and I sure was pissed that he never told me when it would have helped me. After that, I really felt betrayed.