bcz there must be only 3 person ..that is grandfather and his son ..and his 1 grandchild who is the son of grandfather\'s son .... hence 1 grandfather .his son and 1 grand son
bcz there must be only 3 person ..that is grandfather and his son ..and his 1 grandchild who is the son of grandfather's son .... hence 1 grandfather .his son and 1 grand son
1.grandfather
2. his son
3.his grand son