Maintainability of a suit for specific performance

Dear Sir-My late advocate's children having been fighting amongst themselves for the assets of their father. The late advocate had purchased a bunglow in his wife's name and had given a declaration to that effect to the income tax and he was taxed accordingly. During the pendemcy of the partition suit the late advocate' wife gifted the house to her youngest daughter. This daughter during the pendency of the suit executed an agreement of sale of the house to a stranger. The suit was decided in which the house was held to be the exclusuve property of the advocate's wife. In appeal the District Court set aside the judgment of the trial court and held the house to be ancestral property. In the meanwhile the stranger has filed a suit for specific performance of the agreement. In view of this judgment, can the coparceners implead themselves in the suit for specific performance or is it necessary for them to file a separate suit challenging the maintainability of the agreement of sale. Kindly clarify