Forged legalheir without our knowledge

My father was a state govt employee .. Father n mother both died in accident in 2009.. The immediate funeral charges was handovered to me with a g.o on my name from the department. Me n my younger sister r legalheirs of my parents.. so we got a legalheir in 2010.. My father has an external affair n she has a daughter of my age.. She n her daughter also claimed for settlement in the office department.. So the department said us to go to court n split n come.. she even in the court they forged that she is the legal wife..after many struggle they came for a compensation.. I too agreed thinking of my sister to get my father job on compassionate grounds.. So I agreed for 4 shares.. me, my sister, external affair n her daughter... Job to my legal sister... So when we go to department for applying the job, the dept told us the lady (external affair) also has given a legalheir including ur names... The lady in 2014 forged n got a legalheir including me n my sister names n stating that she is the legal wife n we r daughters of second wife.. so then we came to know the truth... Kindly advice us wt should be done to cancel the forged legalheir got by her including our names Ps.. My father dint note anything in his service book..