What is the ruling of Islamic law concerning the grandfather and the stepfather taking possession of the deceased father's money?

Your grandfather (your father's father) is entitled to one-sixth of your father's inheritance, and your mother to one-eighth. The remainder is for the children, with the male receiving the equivalent of the share of two females. If the grandfather takes his share and uses it to marry off your uncle, there is no blame on him. However, if he takes the share of others, it is not permissible except with the permission of the rightful owner, provided they are an adult and of sound mind. It is not permissible for a guardian to dispose of the orphans' wealth except in what is in their best interest. He may, however, consume from it reasonably, commensurate with his efforts, if he is poor.