Rules related to partition after mutation

We have Family House and it's on our Great Grand Father's name. He had two children my grandfather and his brother. Later he got married again after the death of our Great Grandmother, from her he had one son who is our step Grandfather. This house was built by my Grandfather but he never transferred it to his name but earlier Mutation (Dakhil Kharij) was on all three GrandFathers and recently same mutation was done for three Family Heads (My Father and Other uncles). My First question is that as Mutation is done between three Family Heads then whether the partition will be performed in three parts equally or two equally then from one half it will be divided to Heads from single mother ? The second question, other families are not ready for Partition. What is the way to initiate and close the process at the earliest?