validity of agreement paper

My uncle and my father had combined property i.e, 10 acers of land. On 20 feb 1993 my uncle forcely siged an agreement with my father (stamp paper 1st page Rs 30, 2nd page Rs 20 3rd, 4th, 5th page 50 paise, 50 paise 50 paise) in 2 copy and 2 his friends sign as witness. My uncle 8 acers and my father 2 acers. Till property is not registered. Shall my father claim 5 acers as equal share. Will agreement valid in court. What is validity period of an agreement?