What is the best way to deal with a son in eighth grade who steals money from his father to give to his friends, knowing that he is intelligent, dutiful, and active, but he lies and swears when asked about the theft, and does not respond to our attempts to find out his motives, despite all his needs being met?

What has been mentioned about your younger brother regarding lying, swearing, and stealing are major mistakes that a Muslim should not be raised upon. Lying leads to wickedness, and swearing by Allah falsely is one of the gravest prohibitions; it is the Ghamos oath. As for stealing, if it occurs while the son is not yet an adult (baligh), there is no sin upon him, but the stolen money must be returned, and he must be punished in a way that deters him from it, while making him aware of the gravity of what he has done, either by encouraging him to seek religious knowledge, or by presenting the matter to one of the shaykhs for advice and discipline. And do not forget to supplicate for him.