Unable to reach common consensus between joint property holders.

My husband and his mom bought a property in 2012 in mumbai, my husband is the first owner while my mother-in-law is the second. my husband had taken a loan from the bank and has been regularly paying his emi. however, we relocated from the country and ever since then my mother-in-law has been living in tat house with my husbands younger brother (my brother-in-law). as we dont stay in that house anymore we wish to sell the house but my mother-in-law and brother-in- law now want to retain this house for themselves.. they are ready to take care of the remaining loan but we have lost a huge amount in the initial down payment and monthly EMIs. a little background..My mother-in-law is a widow, my father -in-law had crafted a will for the family, in which he mentions equal distribution of assets between all 3 successors (my mother-in-law, my husband and his brother), this includes immovable assets and the cash amount that came through his insurance policy. my questions: 1. does the first owner of a property have any superior right to the property as compared to the second owner? 2. in case of a dispute between selling or retaining a property between joint owners, what can be the solution? (i have read in similar posts that co-owner can sell his share without the consent of the other owner, but i dont understand how is it practically possible to sell any part of the same house?) 3. the insurance amount that was received after my father-in-law expired , does the entire sum legally belong to my mother-in-law even if my father-in-law made a will that clearly mentions that the insurance amount should be split 3 ways between my mother-in-law, brother-in-law and husband? 4. lastly in such cases, what according to u Sir, should ideally be done?