An endowment for children: if one of them dies and he has sons

Question:
He says: Honorable Shaykh, may Allah grant you success. If a father makes an endowment for his direct descendants and the sons of his direct descendants, and his direct descendants number three, and one of them dies leaving sons, do they receive from the endowment while the remaining direct descendants are still alive?

Answer:
It differs. If he says, “For my children and the children of my children,” using the conjunction “and,” then the children of the direct line and the children of the sons share in it, because the conjunction mixes the groups. But if he says, “This is for my children, and after them, the children of my children,” or “then for the children of my children,” this implies a sequence. As long as there is even one person remaining in the first group, it is given to him. If the first group is extinguished and no one remains, it passes to the second group.