Buy litigated property

There's a building with land measuring 1614sq ft. its a 3 storeyed building. this building was entitled to mr.A during 1960s. Mr. A had 2 sons and 5 daughters (all daughters now married and independently settled). Mr. A gifted this building with land to his two sons Mr. X and Mr. Y . on the ground floor I am a tenant encumbering area of 350 sq.ft for my office use. Mr. Y was my landlord and took his rent from time to time. Mr. Y passes away in 2013 in unmarried condition having no wife or children thereof. Mr. A and Mrs. A are also now no more. After Mr. Y's death Mr. X was leaving on the 3rd floor of the said property since his birth and all other floors being vacant except my 350 sq ft office at ground floor. Recently Mr. X sold the property to a neighbour person stating him as the sole owner of the property. After 6 months of such sale and on such information , the rest 5 daughters of Mr.A i.e. Sisters of Mr. X and Y comes and claims rent from me telling me about their share in Mr. Y's half share of building after Mr. Y's death. The third person who buys the full property has not taken the possession yet nor has issued any notice to me stating his legal right over property. questions- 1. Are the 5 daughters of Mr.A i.e. 5 sisters of Mr.Y are legal owner of the said half portion building (undivided property yet) after mr. Y's death? 2. Is the sale of the full property by mr. x right ? if not, shall the agreement be void or void to the extend of mr . x's share in the property? 3. Can the 5 sisters sell their part in the property to any other person now too (if they have their right to the property)? 4. if yes , if i am willing to buy such shares from the 5 daughters...is it legal or will it be good enough on my behalf? 5. as a tenant what should be my step at this moment? if its legal , in good terms and faith, and good on my behalf--should i go for buying the 5 daughter's share or should i not and continue as a tenant? 6. can undivided property be sold ? (my confusion arises beacuse how will a seller mention in deed about the size and specification of the share in property as being undivided)?