forgery/cheating

my father purchased a property in the year 2002, house registered in my mother's name.Title could not be cleared as the land was allotted in seven persons name and all six has transferred it to seventh one by power of attorney. registration could only be done with three out of seven. recently a step brother has filed a criminal suit against his brother who sold property to us that he obtained their signatures on the promise to pay 50000 in the year 1999 which he didn't pay and further while transfer of property in 2005 the thumb impression of his mother is false as she expired in 2004.Now the seller says that all documentation on the subject has been done by the purchaser and he happens to be my father who is presently in coma.I remember all claims of seller is false as it couldn't be,the seller has to make clear his documents before selling and he agrees it in the sale agreement. I want to out of this issue, tried of the court settlement but didn't materialize. further I also want to file a case against these two brothers and the property dealer who sold this property to us for misleading and overall harassment on subject.could you please advise on the issue?