Share in registered gift property

Dear All, My great grandmother had a property in her name which she had bought. The said property is in her name. she had one son and my grandfather has three son, there are other property which my great grandmother bought in the name of my grand father. In the year 2000 my great grandmother gifted this property to my mother and it was a registered gift. now after thirteen years (2013) one of my cousin has filed a partition suit for this property. He is asking for a share in this property which has been gifted to my mother by my great grand mother. I am wondering whether a property in which my great grand mother was the sole owner and she executed a registered gift deed in favour of my mother, can be partitioned? Please advice.