Unequal partition of family (among 4 sons) while the father is st

Hi, i have a property dispute going on in my family since last 2-3 years. my grandfather owns a property in uttar pradesh which has to be equally divided between his 4 sons. But the partition made was unequal. the current scenario of my family is my oldest uncle has passed away, my father's second elder brother is a well settled engineer in Delhi (really well settled). my father moved from our hometown to delhi due to sudden collapse of his business there and then started a new business in delhi 5 years later.and the youngest brother of all is still in home town (well settled). my grand fathers property is divided in two parts first is our house and second is the ground (both of same area).the partition was made like that that my grandfather's two sons who live in delhi get the ground worth 30% of the total value of the property and my eldest aunty (the widowed one) nd the youngest uncle got the rest (40% and 30% resp. ) . this was the decision made by the now eldest uncle the the youngest brother have his bussiness there so he must get more.(not a good reason at all). the ones who live in delhi (i.e. my father and his elder bro) must give 10 lakhs and 5 lakhs each to my grandfather and the eldest aunty(the widowed one). now the problem arise here, the seller to whom we have sold the backyard (i.e. the part by the sons who lives in delhi ) is not able to give the amount by which the deal was made. so now as my grandfather who is still alive and was (bcs the partition is alredy made )the whole sole owner can alter the decision , so that he could now do it equally.