Illegal occupancy of an apartment

Sirs, My eldest uncle (My father's eldest brother) built a three storied house in Kolkata for which a Will was made by him in proper procedure. It was stipulated in his Will that the ground floor was left for the use of my father's sister's family (as she was the housekeeper and caregiver as my aunt - the wife of the testator had been dead and my uncle had no children) but only until she was alive. The Will expressly stated that my father's sister's family would have no absolutely no rights to the apartment once she died and after her death, the apartment would pass on to my younger brother. My father's sister died in 2014 but her son has not still vacated the premises - moreover he has demanded money for handing over the key on the ground that his family has been denied even after giving my uncle such care. The Will has not been put up for Probate as yet. my question is, how can I force him to vacate the premises and have the key handed over to my younger brother who is the rightful owner of the apartment in accordance with my uncle's Will? Can he contest the probate of the will on the sentimental grounds and ask for money for handing over the key to the apartment to my younger brother?