In the case of a devise to the children of A, not in terms executory in character, the children who are living at the time of the testator's death are prima facie the beneficiaries of the devise, to the exclusion of children afterwards born.17 If, however, a devise to "children" is not to take effect immediately on the testator's death, but is in terms to take effect in the future, whether or not a previous estate is limited to another, the same rule applies as in the case of remainders,18 and each of the children living at testator's death will prima facie take a vested estate, subject to divesting pro tanto in order to permit others thereafter born to share in the benefit of the devise;19 and the same rule applies to gifts to grandchildren, brothers, nephews, and other classes of relations.20