Grandfather actually. Ivan III (Ivan the Great) did have a son named Ivan but he was called Ivan the Young and did not rule. Ivan the Great was succeeded by his eldest son Vasili III who was then...
he united many of the independent provinces and succeeded in freeing Russia from the Tartars and became the first Russian sovereign
No, his father was Vasili III
Ivan IV was called Ivan the terrible cause his temper grew as he got older. Ivan also killed a lot of rich people including his eldest son.
Ivan IV, the Terrible, was the grandson of Ivan III, the Great.