How is the share of the mother, relinquished to her three grandsons, to be divided: equally, or with the male receiving the equivalent of two females' shares?

If the granter or endower does not specify a preference for male over female, or vice versa, in the gift (hiba) or endowment (waqf), then the ruling is one of equality. The grandmother's share is divided equally among her grandchildren (males and females), as long as she did not specify a distinction between them.