Grandfather sold the 3 acres land past 18 years ago.

My grandfather purchased the land and Fearing that we could not go to our land due to the sale of others land who are in near to us, grand pa sold the land in the year 2000 with green bond and my dad also signed and my sister has 13 years old and me 10 yrs old but not signed. My question is:- 1. Green bond is enough to make a sale deed. 2. Grand pa property will not claim by grandson and grand daughter. 3. we will win, if we raise the case against party who is in position. Kindly need your valuable suggestion to step forward.