All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
The one who has the right to preserve the wealth of a minor after the death of his father is the person that the father entrusted to act as an agent on his behalf before he died. The custody of the boy by the brother, or uncle, or mother cannot be proven except by the father's will or by order of a court.
The Shaafi'ee scholars said: 'The mother or relatives have no right to be the guardians of the child except by the father's will. However, the relatives from the father's side have to spend on him when nurturing him and educating him even if they had no will for the custody of the child.'
Moreover, the Hanbali school, in one narration, are of the view that the mother has the right for the custody of the wealth of her minor child (children) after the death of the father and the trustee. Al-Buhooti said: 'Al-Athram asked Imaam Ahmad about a man who died and had minor heirs, what should be done? He replied: 'If they have no trustee but they have a caring mother, then it is the mother who would be in charge of the inheritance.'
Therefore, if the relatives of the father's side fear that the mother is extravagant and wasteful of the child's wealth, because they know her as being so, then they should not give his wealth to her, and they should take the matter to the court to appoint a trustee for the child's wealth. Besides, the relatives of the child have to spend on his education from his wealth.
As regards the division of the inheritance of a person who died and left a mother, a wife, a son, two sisters and two brothers, then it should be as follows:
The mother gets a sixth of the inheritance.
The wife gets one eighth portion of the inheritance.
The remaining of the inheritance is to be given to the child. However, the brothers and sisters have no right in the inheritance because of the existence of the son.
Allaah knows best.