Procedure on getting property transferred in grandson name

My grandfather and his brother jointly bought land in 1950s in rajasthan. They partitioned it in two plots and made their houses. Now my grandfather have 3 kids, my father and two uncles, both of them live in kolkata. Cut to today we want to build a proper house on that land and want to raise house property loan but we don't have ownership papers. my uncles are ready to give up their share to us but the problem is we don't know how to get property on their name first and then the transfer to our name. All we have is patta of the plot, that too of combined plot of both our grandfather and his brother's part of the land. The reason to find a solution which just lets us have our part of the land without disturbing my grandfather's brother's family.