What is the ruling of Islamic Sharia on the incident of an "almost insane" uncle sexually assaulting his nephew, taking into account the reporter's fear for his sick grandmother and his children from the uncle?

If the person mentioned is mentally incapacitated (of poor understanding, confused speech, and corrupt management), then there is no punishment for him and no benefit in reporting him, as he is not held accountable. However, if he is of sound mind and committed the act of sodomy, and this is proven by four witnesses, it is not obligatory to report him. Rather, it is requested to conceal his act, admonish him, and warn him, because concealing (faults) is obligatory for a Muslim, both concerning himself and others. Care should also be taken to protect the children by warning them against approaching him and monitoring him.