Unjust division of property dispute.

My grandpa passed away in 2011 without dividing his property and without any will. We live in a joint family in the same property but there are disputes over property division every single day in my home, in order to accomodate family members needs. My grandma is a widow and has 4 sons living in the same house. However, the property occupied is not equally divided among them. My father being the youngest son faces deep trouble since he is being discriminated against by his elder brothers. There's no sign of justice in their eyes and we face these fights on a daily basis. My uncles are encroaching upon our portion of the property and are not ready to divide it equally because they have bigger families in comparison to ours. They want more share only on this pretext and have joined hands with each other to disregard our rights. They even measured the property as per their convenience. We have already given them an extra share from our property still there's no end to their tactics and unscrupulous behaviour. Please let me know how should I proceed in this scenario and help out my father to get his rightful ownership. I am all ears for your suggestions.