My grandad did leave a will, but strangely no-one could find it.
Basically, Sis's sister did what she did to spite those who had suggested before my grandad's remarriage that he might be being hasty in wedding his put-upon, equally-old next-door neighbour on the rebound after the death of his wife of 44 years. Rather than proving them wrong, Sis's sister proved them right.
It's absolutely correct that a wife inherits everything from her husband (and vice-versa) and that thereafter she can decide to do whatever she wishes with it. If Sis wanted to make sure my dad and his brother received nothing, well that was the end of the matter. I suppose my dad or uncle could have invoked a lawyer, but all my dad wanted were the family photos and the books he had as a child; my uncle's main concern was that his collection of Dinky toys (still in their boxes) be returned to him. A lawyer can't do anything to recover goods that have been either burned or thrown out, though.
The only thing my dad managed to get hold of (I'm not sure how, but it could have come via his brother) was my grandad's trilby. It therefore bore some significance for him. When my dad died earlier this year, it was given to me.
It would seem that my grandad's head was somewhat smaller than mine. Still, it's not about wearing it nor not, so I'll be keeping it. My dad didn't wear it, either, which is evidenced by the fact that it's in very good condition for something at least 41 years old.
I suppose my dad and his brother could have put in a claim for a share of the house when Sis died, but my dad at least was never told when she did die. My uncle might have heard, but in the fallout from my grandad's death he became estranged from the rest of the family so wouldn't have told us even if he had.