1) grand mother was absolute owner of property . i presume she died intestate ie without any will .
2) on her demise your father family has 50%share in said property and your uncle has 50%share in said property
3)you can file suit for partition . your father share would on his demise devolve on his wife and 5 children . in other words you have 1/6th share .
4) issue legal notice to your brother . if your brother is willing deed of family settlement can be entered into failing you will have to file suit for partition