Marinus I was the Duke of Naples from 919 to his death. He was the second son of Gregory IV

Gregory IV of Naples

Gregory IV was the firstborn son of Duke Sergius II of Naples and successor of his paternal uncle, Bishop Athanasius, in 898, when he was elected dux, or magister militum, unanimously by the aristocracy. His other paternal uncle, Stephen, succeeded Athanasius as bishop...

 and successor of his brother John II

John II of Naples

John II was the duke of Naples from 915 to his death. He succeeded his father Gregory IV on the latter's death late in 915.He had accompanied his father to the Battle of the Garigliano under Nicholas Picingli, where the Christian coalition defeated the Moslems of the fortress on the Garigliano....

. The Chronicon ducum et principum Beneventi, Salerni, et Capuae et ducum Neapolis calls him Marianus. According to that document, he reigned eight years, nine months, and fifteen days.

Marinus was succeeded by his son John III

John III of Naples

John III was the longest-reigning Duke of Naples . He was the son and successor of Marinus I.At the beginning of his reign, he warred against the Saracens and then made a treaty with them after they appeared beneath his walls in 929...

. He left a daughter Orania who married Docibilis II of Gaeta

Docibilis II of Gaeta

Docibilis II was the ruler of Gaeta, in one capacity or another, from 906 until his death. He was the son of the hypatus John I, who made him co-ruler in 906 or thereabouts....

 and brought him Cimiterio and Liburia as a dowry.

Sources

• Gay, Jules. L'Italie méridionale et l'empire Byzantin: Livre II. Burt Franklin: New York, 1904.
• Foundation for Medieval Genealogy: Southern Italy.