How to file a partition suit for property

May father died in 2010. Me, my sister and my mother are his heirs. He had two lands in his name. One land is non-agricultural land of 8.92 Acre, now our three's name has been mutated on the 7/12 extract of the land. Second land is an agricultural land of 10 acre, which was jointly held in name of my father and mother, now father's name has been replaced on 7/12 by mine and my sister's name. Both the lands are in separate tehsil/ taluka of Nagpur district. Thirdly we have an ancestral house (on NIT plot) in Nagpur city still in name of my grandfather who had died in 2009, he has left a will giving 25 % share to my father. Now my sister and her husband are demanding half of the share of property which is in my mother's name (while she is still alive) to be gifted to them. My sister has already got 33% share in the property but she is demanding 50 %( by including half of mother's share). Me and my want to file partition suit for the property. How to solve the problem?