All perfect praise be to Allah the Lord of the Worlds. May His peace and blessings be upon Prophet Mohammad and upon all his family and companions.
A woman doesn`t have the right to demand dissolution of marriage because one of her husband`s relatives suffers from a certain disease. Moreover, even if the husband himself suffers from vitilgo, it isn`t permissible for the wife to demand divorce because this disease is non-contagious. Thus, demanding divorce from husband because his maternal aunt has this disease is ridiculous. Actually, the right to demand dissolution of marriage in case the husband suffers from a contagious disease is the wife`s alone. However, if she accepts her husband as he is then her family has no right to force her to demand dissolution of marriage. Based on this, there is no evidence in Sharia that bans the continuation of this marriage.
Finally, we remind that the Messenger of Allah (Peace be upon him) said: "He who makes a wife disaffected towards her husband or a slave towards his master is not one of us.” {Related by Abu Dawud}. And Allah The Almighty Knows Best.