Disputed property sale

Sir a piece of land measuring 2000 sq ft was given by my Nani through a registered will 1/2 to my mother and 1/2 to my chachi/maushi as two sisters were married to two real brother in 1972. In the year 1980 chachi/maushi expired in fire accident.Have only son and a daughter. In 2009 her son also expired issuless with one adopted son.In the meanwhile my father took some construction work with consquent of my chacha/mausha taking galary in the middle of the plot and stairs in 1989 to use stairs jointly.Every thing was right till the year 2005 when my father was alive.The whole 2000 sq ft area is in over possession we are paying all house tax electricity,water bill since 1972.No due to price high my chacha/mausha is selling to 1000 sq ft area to other pers and forcing us to remove out stair built in about 4* 15 ft.1. Whether he can sale the said land dividing the portion as per will. Secondly under HACK A MAURASHFA we can claim it our right to purchase first as per govt guide line market price Can I take a STAY from court as at one mediation center he asked the permission to built the said area.Further in the SDM court he was ready to leave that 60 sq ft area.Court order copy is with us.thirdly If he sales the said land to third party he can remove my stairs.I shall be highly thankful for your valuable advice.to this disabled ex army soilder.