Who inherits our deceased stepmother, who has no living sons or daughters, but has two grandchildren from a deceased daughter, a deceased full brother who has descendants, and a living half-sister from the father's side, knowing that she previously desired to gift her share of the house to her two grandchildren but did not document it?

The two grandchildren (the daughter's son and the daughter's daughter) have no share in their grandmother's inheritance, because they are not among the inheritors, but rather among the relatives by blood (dhawu al-arham). The inheritors are: the paternal sister, who receives half as a prescribed share (fard), and the remainder goes to the males among her full brother's children by agnation (ta'sib).