A room under a thika land and land owner putting up too much laws.

There were 4 (A,B,C,D) brother and 2(Y,Z) sister as actual owner of the property they all five died, alive is only a sis(Z). Only brother(A) has successor(A's) and a sis(Y) had a son(Y's). Sis (Z) is alive & still single and too old to get marry. 1. I actually dont know who is the legal owner of the property and who is my actual landlord. 2. The son (Y's) is staying with her wife and kid with his aunt (Z) and taking care of rent and bills and all the room that I am talking about the room that was my uncle's and now he got the room transferred under my name for that I paid 40K to acting landlord(Y's) beside that he want me to get under an agreement where he mentioned a. the rent will be increased to 10% every five year or on mutual talk which ever is higher b. i cant sub-rent the room to someone. c. i cant use this for commercial purpose. Its a "tin ceiling" a small ground floor room I may need to use it for some commercial matter. please advice me if the "Y's" point raise is correct and backed up by law? if not what are the references i can ask him to refer we own that room for almost 40 years from now (Y's was not even born then). please help and advice. please help