Dividing paternal property

My father died four years ago without leaving any formal will. My mother never had any experience of family administration as my father used to be all in all. We are four brothers and two sisters, of these the second youngest brother passed away some ten years ago leaving his wife and three sons. I am the eldest (boy) in the family, I had gone abroad for studies, training and work for many years, in fact I ever hardly stay at home except for holidays. I married late and have two young children (14 & 12 yrs old) My next brother is a retired school principal with a number of children and grand children. The third is a sister who has been with my parents longest and the one who assisted them in the business. Her daughter is my dad's favourite too. The fourth one is a brother who left his high paying job with a company in order to be with my aged parents some ten years ago and he is single. The last one is a girl who has been living abroad with her family for the past 20 years. Now the problem is: since my father did not leave any will, my sister (elder one) and the youngest brother, both of them who are at home, claims that the business as well as the big property (some 15 acres of land) will be taken care of by them(meaning will be theirs) while myself and my next brother are given to divide a small plot of land in the city(3500 sq ft) between us. Of course there is nothing left for my deceased brother nor the younger sister. My mother is unable to say anything in our favour as she is dependent on them. I would like to know in what way can we legally or whatever settle reasonable to the satisfaction of all. Kindly advise.