@islandgirl,
Her work has come into greater value only after her death? Is she a "regional artist"?
Why did only he choose your mothers artworks and noone else? This sounds a bit like you were snookered by someone who was more art saavy than you and your other siblings.
The smart thing,at the time, was to have the stuff appraised, the valuable and the not-so-valuable, then you should have divvied up in more equal portions.