Partition: implead 3rd parties who are in possession?

parition implead 3 parties who are in possession? 1.My uncle has filed partition suit for 2 properties belonging to my grandfather and I am one of the defendants. 2.I know two properties are in possession of 3rd parties. In one property the old house has been demolished and flats built.In Court the property is shown as vacent site 3.Another house is vacant and locked. People living nearby say my uncle no longer lives there although in court he provides that address. Registered post to that address is returned with "addresse not found".Through RTI I found there is another municipal no for the property but all efforts to get info on that revenue account have been stonewalled. 4.I have not yet been able to trace the original sale deeds since the properties were bought in 1930s and the municipal nos have changed 3 times since then. 5.My advocate says 3rd parties can be handled in subsequent case and nothing needs to be done in this case. 6.Other advocates have said I need to act and seek court direction and implead the 3rd parties. Do the 3rd parties need to be impleaded? Or should I file separate case later? Can I force my uncle who is plaintiff to submit possession records for the properties? I have tried to obtain the records through RTI but it is pending in courts Can I force that the possession status of the properties be on record before proceeding with the partition suit? gokul