We need father like this

You should try to bring the same to the notice of the elders of the family so that an amicable seperation and good settlement for your sister can be worked out.  This is assuming that your sister wants out of the marriage.   

Sorry to hear all this about your sister. However if the husband is unfaithful with your sister, I think continuing the marriage with such man is of no use. The dissolution of marriage by mutual consent after settling the permanent alimony and maintenance for wife and maintenance for both minor children till the time they continue their education and are able to secure independent job for themselves should be sought from this man. Going for years long litigations both civil and criminal leads nowhere.

​As far making him understand the value of marriage and family life will not serve any purpose as he has been completely brainwashed by his female friends and bad habit are difficult to be given up

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