cutting the ties of kinship is one of the major sins, as the Prophet (peace be upon him) said,
A breaker of kinship ties will not enter Paradise.
(Related by Muslim.) He also said,
Al-Rahim (the ties of kinship) takes hold of the Throne and says: May Allah maintain those who will maintain me! May Allah sever those who will sever me.
(Related by Muslim)
Taking an oath to sever the ties of kinship is an objectionable statement. Furthermore, prohibiting that which Allah permitted, including wives and lawful property is Haram (prohibited) and transgression against Allah. You should ask Allah's forgiveness and perform Tawbah from severing the kinship ties, taking an oath to do so, and prohibiting that which Allah permitted. You should regret your past sins, keep your kinship ties, and repel the evil of your brother with good treatment. It may be that Allah will accept your Tawbah and forgive you.Secondly, if you maintain kinship ties with your brother again, you will have to offer a Kaffarah (expiation) for an unfulfilled oath. (Part No. 25; Page No. 317) You have to feed or clothe ten needy people or manumit a believing slave. If you can not afford to do so, you will have to fast for three days.Thirdly, if you intended by making your wife unlawful to you that you assert and prevent yourself from maintaining kinship ties with your brother and that you did not mean divorce or making her unlawful, you will have to offer a second Kaffarah when you restore your relationship with him. The Kaffarah of the unfulfilled oath is mentioned above. With regard to your property, it is not prohibited by your said statement.May Allah grant us success. May peace and blessings of Allah be upon our Prophet Muhammad, his family and Companions!