Praise be to Allaah.
With regard to the question of marriage, if you have any authority or influence over your brother and can convince him to give up the idea of marrying this woman, then remember that the Messenger of Allaah (peace and blessings of Allaah be upon him) commanded the Muslim to marry the woman who is religious. This woman is sinful and goes against the religion, she is not modest in her dress and she drinks wine, so he should not marry this woman.
With regard to the issue of his disobedience towards his parents, this sin is more serious than the one mentioned above. They have told him to obey Allah and to keep away from sin, so he must obey them and avoid going against their wishes. Your familys rejection of this marriage is quite correct according to shareeah, because they are enjoining what is good and forbidding what is evil, and seeking to control one who is insane.
It is permissible, indeed it is necessary, to forsake him if doing so will stop him from going ahead, because marriage to this woman will keep him away from his religion. In America and in other kaafir countries there are many individuals in the Indian, Pakistani and Arab communities who have forsaken their religion and are no longer Muslim in anything but name.
As regards depriving him of his inheritance, this should not be done unless he becomes an apostate (leaves Islam). So long as he is within the pale of Islam, and does not do anything to put him outside of Islam or to make him a kaafir, then it is not permissible to deprive him of his inheritance, because this is something prescribed by Allaah, and as such it is not permissible to change it. And Allaah knows best,