Husband is insane from last 10 years want divorce from wife

Hello My uncle is not in normal condition from past 10 years. When he got married in 2001 to my aunt who is in Police.At that time he was in his well state of mind he was not working also.They both have a girl child as well who lives with my aunt.After few months of marriage she went to Varanasi to join her duty and all. She used to come home on weekly or monthly basis. Passing years on one 31st December my uncle went there to live with her but when he came back from there he was not in his normal condition. He was rude , brutal that he could do fight with anyone even he could slap and then one day he went somewhere without telling anyone coz he had lost his mind (mental condtion ) after one year through one unknown letter we gpt his address then we got him back In this whole one year my aunt was living her life without any worries she dint even bother to ask that is his husband is alive or not ? We as family also belive that coz of her only and only she is responsible for his mental condition. She dint even talked about anything last she visited us when my grandfather died for two days , and there also she just talked nonsense. After that she is having baby boy to whom she call that he is adopted but God only knows. People say and we that she married also to one of his police colleague. My uncle lives with my grandmother in village on regular medicine. Now after so many years she renter in our life as she sends her daughter to my grandmother house just for seeking enquiry and all that whose alive what's the condition is . She is such a greedy woman that even we doubt that she is definitely suffering in her life this is the reason that she is knocking our door again. Could you please tell us that is there any way to keep her out from our life via taking divorce ? Is there any possible thing which can be done to save our uncle life from that cruel woman?