No, the widow does not get everything if the deceased left an estate over �200,000:
# f there are parents, brothers or sisters of the whole blood, nephew or nieces:-
* Spouse gets everything up to *�200,000 & personal possessions.
# Anything remaining is divided into two:-
* Half of this goes to spouse
* Half to parents. If no parent is living then it goes to brothers or sisters or their children.
Remember though that if there is a house, and it is owned as a joint tenancy, this is excluded from the value of the estate - it is the widow's own property.
You say your brother wanted his nephews to inherit, but without a valid will they won't.