Harassment of daughter in law on mother in law and entire family

It's been more than 2 -1/2 months my brother's wife left our house with no reason along with his son who is 6-1/2 years old.Since then she stopped calling us neither allowed us to talk to my nephew.Her two elder brother threatened us for filing divorce which they haven't done yet.Just they sent us a formal letter from Advocate that she wants to get seperate again with no strong reason.My mother who has nurthured my nephew since his birth is getting weaker day by day due to stubborn ness of my brother's wife.For more than 6 months their was change in her behaviour which made us shocked but at the same time my parents who are senior citizen neglected her wierd behaviour that will understand one day because it's been 9 years of marriage.Her two brothers are making my nephew as a tool to harass us at any cost.First one month they kept on changing their statement towards their demand.As their family are aware that my nephew is the weak point of our love and affection specially my aged parents, they are going too far to harass us as not a single legal action they had given us.Need ur assistance whether my parents can file compliant on her as it is deteriorating their health physically and mentally as well.