My son is occupied my own flat..in mumbai.

Resp.sir. i am 83 year old senior citizen, i have total 4 sons. but i am staying with three of my son partly and they are taking care of myself in all manners very well as per there capability. from that 4 of my sons one the eldrest is not keeped any relation with me and even with any brothers. Sir, i have one flat in mumbai which is totally owned by me from last 40-50 years.and we all stayed in the same as joint family. but as time changed three of my sons separated and start staying with there family. before 15-17 years, but my elder son was continued staying in my flat and all of us were agree due there were no issue, hence from last 15 years all my three of my son partly and they are taking care of myself in all manners very well as per there capability, but my elder son even not bother to ask atleast about my health. Due to my health reason i have decided to sell the flat and distribute to all my sons equally...but my elder son is denied to accept the option..and says he will not vacate the flat..and if myself or any brother will try to do so he says us to keep ourself to face dire consequences. you are requested to please guide me the way that i can do the real true justice for all of my sons.