Need to know how to proceed with divorce without mutual consent.

Dear Sir/Mam  . This is regarding my younger brother. On 30/apr/2015 My brother got married and after few days of his marriage his wife told that she did not like him and his family and want to go home for forever. we got afraid and thought that might she blaim us for dowry . So for precaution I write a note in which I mentioned that She is going by her own wish and their is no demand of dowry from our side . The reason for leaving home is that she did not like her husband and family of her husband. She signed that note and her father also signed as a witness. after 4 months her father called us and said that she was not well at that time thats why she told all these things . and now she is ready to come. We agreed and take her back to our home. But her behavior was not good towards her husband and to our family . But we ignore that behavior. In December 2016 she become a mother of a baby boy. but after one month she again started same