Rights of second wife

Respected sir i was told by my husband that he has been divorced from his first wife and he had two children that time of my marriage one girl age(3.5yrs) and boy age(1.5yrs). the two children were bought up by me till to date. i am having one girl child, now age is 21. after my husband passed away in an accident. Suddenly the first wife is appearing after a gap of 25 years and trying to take all the benefits. where else i don't know about it very clearly. but my husband has entered my name in his ration card and also in railway records. i am completely uneducated my daughter is writing this letter, her own children are against her. she and her family never appeared in front of us and never filed any complain on my husband regarding children custody or maintenance. she use to be very cruel with them. her own daughter(married 28 yrs) is scared of her till to date. she even din't appeared for her own daughter's marriage. sir i don't expect money from court for my sack but please tell me a way so that my three children's can be benefited and how i can protect them from her.