Adverse possession claim / Ancestral property claim on property purchased by me

I am a Rt. Govt. teacher. Being a govt. teacher, I got a land in 1969 from govt. in teacher’s colony on lease rent of 30 years. I was unmarried at that time and in a good faith I allowed my father to built 2 room-kitchen on my land so that my family can stay there. Later my father passed away and I got married and shifted to another city in 1985. Since then house is in the possession of one of my brother (staying with my mother since 1985). Now they are not ready to vacate the plot and another brothers are also claiming their rights on the property. My brother is operating one shop on my plot and has somehow managed to get electricity connection of the shop on his name (don't know how). He might also be paying property tax but I have clear registry as plot was only given to govt. teachers that time. My questions are: 1) Can they claim property on “adverse possession” ? (I am allowing them to stay just in a good faith till my mother lives – 90 years old, I do not have anything on writing) 2) Can they claim property on ancestral basis ? (Since they are saying that my father has paid for construction over property) 3) I am 70 years old. Can my case go into fast track, if i initiate anything now ? and if yes how much time (approx.) it would take to get justice from court ? 4) They are in possession of registry also and not giving me back. I am unable to renew lease rent also and they are pushing/pressurizing me to negotiate on 50-50 share, if we mutually sell the property. 5) What are my chances of winning the case in this scenario ? Need some concrete opinion / advise, since amount involved in the property is high and no action is being taken by me since I left that place in 1985. They have good contacts and relations in that place as they are localite.