What is the ruling of the Sharia on a father who registered a residential house in the name of his grandson without the knowledge of his two sons, who only found out about this after his death?

The grandfather registering the house in the name of his grandson can fall into two categories:

Either it is a will to be executed after death. In this case, the grandson does not inherit as long as the grandfather has a direct son. The will is executed for one-third only, unless the heirs agree to an increase.

Or it is a gift made during the grandfather's lifetime, which has three possibilities:

1. If the gift was made while the grandfather was healthy and the grandson took possession of the house, then the house belongs to the grandson. 2. If the gift was made during a life-threatening illness and the grandson took possession of the house, then it takes the ruling of a will, and only one-third of it is executed, unless the heirs agree to an increase. 3. If the gift was made while the grandfather was healthy but the grandson did not take possession of the house before the grandfather's death, then the gift becomes void.