Common passage between partitioned land

We have an ancestral property partitioned between my father and his brother. Plot is 48 feet in width and around 260 feet in length. There are other building on north and south. On east there is a 20 feet road and on west there is a 8 feet narrow lane. There are other building south of that narrow lane. During partition, there were 4 shops constructed by the east side road and there was a 8 feet passage in between to reach the remaining land which was being used for agriculture purpose that time. With partition, both brothers got 2 shops each and the passage remained as it is with 4 feet from both parties. After partition, over a period of around 30 years, my father constructed 3 buildings in our part of land facing the common passage. 24 families live in those and use the common passage. Sometime in 2010, both parties also did an agreement on Rs. 50 stamp paper over agreeing to have the common passage and to clarify that neither party will do any construction on the common passage. My uncle's part of land is still vacant. We are not on good terms and he is now insisting on giving a wall in between. With wall the passage will only remain under 4 feet for each one and that would be a loss for both. But because uncle's part of land is still vacant, he will have the option to later construct in his own ways but for us there will be no option and all those families living in the building complex will have to adjust to around 3 feet passage which will have poor ventilation etc. Question is - What does law say in such scenario?