Undivided Land used for Residence

My grandfather had 6 sons. Before he passed away, all the sons stayed together in a undivided 4200 sq ft land. After his demise, three of the sons migrated to other state to earn livelihoods. My father and two uncles with us, the grand children, stayed there for good 25 years. One of the uncles staying there moved to a different place to a flat bought by his sons. That left my dad and an uncle at this property. In 2012 the uncle staying with my dad had to marry his son. As the house was very old and in a bad condition, he constructed a G+2 on around 1800-1900 sqft area. It was more of an understanding between all the brothers and no one objected. Since, this was the only residence we had, at the time of my marriage in 2021, June, we also constructed a G+1 and a half in 900 sq ft area and as it was for our self use rather than deriving any income, again no one objected. Now, one of my uncle's son staying in his own flat in a different city wants to file a partition and sell off his share to which i do not have a problem. There is a remaining part of the property close to 1400 sq ft which is in a very bad state as it has been left unrenovated after my uncle and us moved in to our flats and neither any of the other uncles nor their children ever came to check. As this is the only place of residence we have and this cousin has given a hint to us that he wants his share in the flat we have made right from foundation with pur money, how do we save the same? Sorry for the long post