Is it permissible to deprive the eldest brother of his rightful share of the inheritance after he sold the inheritors’ properties and did not pay the debts, in addition to other actions he committed? And is it permissible to give his share to his first wife and their children?

If your brother has wrongfully taken your money, it is permissible for you to take his share of the house up to the amount of your right or less, without giving it to him. If his share exceeds your right, you take your right and return the remainder to him. This issue is known as "Mas'alat al-Dhafar" (the issue of taking one's right by force), and it permits a person to take their right from the wealth of one who has wronged them, if they are able to do so, regardless of whether the property is of the same kind or not, and whether the debtor knows or not, without the need to refer the matter to a judge. This is conditional on the right not being a punishment, and that one is secure from discord and depravity. You are not obligated to pay his share to his wife and children, as the money is your brother's and you have a right in it. If you do pay, it is an act of kindness and charity on your part.