Inheritance of property

I have a friend named Raghu, He had two elder sisters (both were married) and an younger brother. Raghu lost his parents 5 years ago. From then One of his elder sister's husband is taking care of them. Both of his sister's marriages was done by her father before his death settling properties as dowry. And his parents made no will about their property. Now, their sisters were asking for the share in the property. (by forces of her husbands) What is their extent of legal right in that property? and who will be the heirs of that property.? Please any one give a solution to this problem.