What is the ruling of Islamic law regarding dealing with a close relative who steals? Is it advisable to be patient with him or to deter him with available means?

It is not permissible to accuse a Muslim without evidence, for Allah Almighty says: (Avoid much assumption. Indeed, some assumption is sin), and the Prophet, peace and blessings be upon him, said: (Every Muslim's blood, property, and honor are sacred to another Muslim). If there is evidence of theft, the thief should be advised and reminded of Allah. Otherwise, he should be threatened with exposure, and help should be sought from someone who can rebuke him. If he does not desist, his case should be referred to the competent authorities. It is not permissible to punish him by beating; because punishments are the prerogative of the ruler and his deputies.