Muslim personal law

Hi,

This is with ref. to an agricultural land (near Bangalore) which we had purchased from a Sunni Muslim family. We had purchased it in year 2002 from 3 brothers of the family. Please note that they also had a sister who was married & used to stay with them during the time of purchase. They had inherited this property from their father. Being a joint family all of them (incuding the sister's family) stay in the same house which is very close to the property. In year 2005 their sister paassed away due to old age. In year 2008 the sister's sons & daughters have filed a case against their 3 uncles & us claiming their right on the property. Please advise us on the same.

Thanks.