All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
If your father meant that his inheritance should not be divided after his death but only after the death of his wife –if we presume that she dies after him –then this will is not valid and the heirs are not obliged to act according to it. Furthermore, if he has heirs other than his sons, like having daughters, then this will is also void because it is a will for an heir. It is known that a will for an heir is forbidden and it is not valid unless all the heirs consent to it. Moreover, preventing the daughters from inheritance is among the traditions of the people of the pre-Islamic era of ignorance, and it is an unjust will. Causing harm (to any of the inheritors) with a will is forbidden and the scholars considered it as one of the grave major sins.
Allaah Knows best.