1. If you admit that your grandmother had recently told you then the Court will say that at least one of the legal heirs of your grandfather knew about the incidence for which he matter will become time barred.
2. Since your father is the legal heir of your grandfather (if he is dead), then your father and if he is no more then his legal heirs can claim that you recently came to know from the occupants, whom you considered so long as tenants ( or labourers, as the case may be), that the said property has been sold to hem illegally by the brothers of your father.
3. Once the suit is admitted by the Court, you have a very fare chance to win it.