Otto was the third son of Count Jobst II and his wife Anna of Gleichen.
Otto married in 1568 to Agnes of Bentheim-Steinfurt, the widow of Count John II of Rietberg, who was also the mother of Armgard, who was the wife of Otto's brother Eric.
[1] Otto VIII died childless on 25 November 1582 at Hoya Castle.
He was buried in the church of St. Martin in Nienburg; his tomb is located in the hall below the tower.
With his death, the House of Hoya died out, and the county fell back to the Duchy of Brunswick-Lüneburg as a possession of Frederick Ulrich first and then of William August.