Ravish has no choice but to keep Vividha in the house as his wife. The day he discloses the facts to the family, Vividha will be thrown out. The family still doesnt know about the presence of Atharv and Sujata in the house, even if they, it will already be a big task for everyone to accept. In this scenario, what is ravish supposed to do? go to this family and be like "hey mom, Vividha and I are going to get divorced and she is Atharv's girlfriend, who is my illegitimate brother and is already in the house, and btw he is retarded now and needs to be cured, so Vividha needs to live in the house. so let her stay" .
Vividha has cheated Ravish and his family, he may have forgiven her and may move on, it will taken longer for his family especially the mother to accept it, and even if she does, why in the world would show allow Vividha to live in the house.
All of you who would now start on atharv have a right over the property and keep Vividha if he wishes to, let us not forget that the grandfather is still alive and probably still has the control over the property, especially the house, and we all know how he feels about Sujata.
Furhter, even if they divorce, i am sure the hindu marraige act probably has clauses that do not let the divorce happen very quickly, so lets wait and stop being judgemental.