Can brother inherit more if mother gifted him everything?

Can a mother transfer her share of her deceased husband's self-acquired DMAT shares, bank balance, and another rented property to her son in an intestate case? If so, can the son technically claim 50% (his 25% share plus the 25% inherited from his mother), while we—two daughters—get 25% combined? We asked for a 1/3rd share each, but our brother insists on giving us only 1/4th. Our mother has already transferred 100% of her assets to our brother. Please advise.