Husband escaping from responsibilities and sending lawer notices

Hi, My sister is married 5 years back and gave birth to a baby girl who is 4 years old. Both my sister and brother in law are software engineers in hyderabad when they married. But, he started acting as sadist from day one of marriage. My sister told things to us only after child birth. He even forced her to go for abortion. When we started questioning he started escaping. She bared all his physical and mental harrassment and we talked it thought with his parents who always supported him. Suddenly one fine day when she have fever he got her to our parent's home which is near by and left her there with the child. Next few weeks he didn't turn up and we came to know that he moved to Bangalore through the landlord of house. I somehow contacted him and talked it though. We called their parents also to hyderabad and talked. They apoligised and asked my fater to move their rented place to other house as old landlord knows the issue with this guy etc.. We fell for the trap and moved her to the house next to ours for rent. When my father called he said he is not coming back and we tried contacting their parents they didn't lift phone. After 6 months now he sent a lawyer notice saying she is staying away from him for 1 1/2 years in my parents place (which is wrong) and asked her to come to Vizag(his native) to stay with him within 7 days of notice. She is working in best possible MNC in india in a senior position and during last 5 years this guy was fired from job 3 times and finally he settled in a small company in Vizag. She is in a position to give good education to kid but looks like his sadism has gone to peaks and started troubling using law. Can you suggest what can be done. One mistake we did is not to report domestic voilence due to my father's good reputation in society.