Case of grandfather property.

My english is not so well so please fogot my mistakes and please understand what i want to tell... My mother is second wife of my father first wife of my father is expire in 1980 from first mother i have one brother and one sister. I am from second wife of my father. My grand son is expired in 1989. My grand father make no any will of his property my grand father have total 5 son and 3 daughters all parts divided of my great grand father property in all sons. My father is expired in 2003 with making any will and now i want to take my part on grand father propert but my cousin brother not giving me share on that property he make 2 floors on that and taking rent from 2003 and not giving me till date today. I want my share please tell me and help me what i do ? And how ? My cousin brother said that the father is giving me all grandfather property to me? My cousin brother said there is no amy share for you i make all the building who gave my money back .. When my brother buil that building i don't know any about that. Building build about some 7 or 8 years ago. I dont' know any thing about it ? He takes rent about till my father expiers and not giving to me any share of rent.