• Suggestion for civil suit and criminal suit

in 1985 my father purchased a extended lal dora residential plot in delhi on his cousin's name through irrecovable gpa with consideration later in 2006 cousin transferred the plot on my mother's name through gpa then in 2009 we came to know that after the main owner ehose name was in mutation died and the same mutation came on his lr's that are his 3 son's in which 2 have sold their share to other person knowing that we are the owner. through sale-deed showing their mutation. we filed a criminal case under section 467,34 and civil suit for sale-deed cancel. we have to file a case against 3 son also or not and for mutation challenge any case so that we can become the owner of the plot in mutation..till now we have not filed any case aginst 3rd son boz only his name is indicated in mutation but he has not sold his share to anyone . and possession of the plot is in our hands..thanks