Property Issue

Hello sir....we are three brothers....the property papers which we have mentions that 50% of the property belongs to my mother who is no more.....and rest 50% belongs to my brothers, i.e. 25% (younger brother which again is no longer alive) and 25% ( the other one which is alive)....and i do not have any share mention in the property.....now we live in a joint family each having his own floor...i live in 2nd floor......now sir i want to ask you i want to sell my own floor and want to relocate to some other place...now what all documents do i need to prepare as in the property papers i do not have my share ( the only share i believe i have is my mothers share who is no more but her share gets divided between all her three sons, i.e. 13%....but my brother has no issue with me in selling the floor where i live..... and another thing is that my mother as well as one of my brother is no more with us...so how can i prepare the documents...sir i will be very grateful to you if you answer my query.....