Is it permissible for a grandfather to manage the pension of his deceased son's daughters by allocating a portion of it for their expenses and saving the remainder for them, knowing that the allocated amount is insufficient for their basic needs?

The person most entitled to guardianship over a minor after the father is the grandfather. He must spend on his grandchildren from the money their father left them, in a reasonable manner, covering all their needs including food, drink, housing, clothing, medical treatment, and education. When any of them reaches maturity, he must hand over their money to them. If the grandfather does not spend on his son's two daughters from their money in a reasonable manner, he is sinful. His saving money for them does not intercede for him, because fulfilling immediate needs is more important. The Messenger of Allah, peace and blessings be upon him, said: "It is sufficient sin for a person to withhold from those whose sustenance he possesses."