Is the questioner obligated to compensate his grandfather for the social security pensions he was deprived of due to the issuance of a commercial register in his name and the change of his profession?

Firstly, if the grandfather authorized the action while fully sound of mind and aware of its implications, then the one who carried out the action is not obligated to compensate for the resulting deprivation of his salary. This is because what arises from an authorized act is not guaranteed.

Secondly, if the grandfather was not lucid at the time of his consent, then his authorization is not considered valid in Sharia. The one responsible for his deprivation of salary must compensate him for the salaries of all the years he was deprived. These amounts shall then be distributed among the heirs according to the Islamic division of inheritance.