How to legally resolve the Property Dispute Between Brothers

Hi Sir/Mam, So there is an issue related to property between my father and uncle. We have a big plot which is in the name of three persons, one is my father, second is my uncle & third is my aunt (uncle's wife). So what my father now want is to get his share of land from that big plot which will be only in his name, now the question arises how that property will be divided will it be divided equally into three parts or in any other way, as such I'm concerned there is nothing in the papers related to the amount of share each person has, it's just that the plot is in name of three people. ? Another thing is that my uncle is not getting ready to separate the property but my father really wants it separated so how can we proceed in that case? And he is also trying to acquire more portion of it than 2/3 which equals his and his wife's share how can we stop that legally? Please help..