Venier was born in Venice around 1496. He was a son of Moisè Venier and Elena Donà, and a nephew of Zuan Francesco Venier, Co-Lord of Cerigo. He was a paternal grandson of Moisé Venier (ca. 1412 - ca. 1476). He was the great - great - great - grandson of Pietro Venier, Governor of Cerigo.

He worked as a lawyer from a very early age, though without holding formal qualifications, and subsequently was an administrator for the government of the Republic of Venice. In 1570 he was procurator and, in the December of the same year, capitano generale da mar ("Chief admiral") of the Venetian fleet in the new war against the Ottoman Turks.

He was the commander of the Venetian contingent at the Battle of Lepanto (7 October 1571), in which the Christian League decisively defeated the Turks. After the peace he returned to Venice as a very popular figure, and in 1577, at the age of 81, he was unanimously elected Doge.

He was married to Cecilia Contarini, who bore him a daughter, Elena Venier, and two sons. One of his sons, Francisco Venier, went to France.

Sebastiano Venier died in 1578, allegedly of broken heart after a fire that had heavily damaged the Doge's Palace of Venice. He was interred in the Basilica di San Giovanni e Paolo, a traditional burial place of the doges.

He was a first cousin once removed of Cecilia Venier - Baffo, known as Nurbanu Sultan after her conversion to Islam, daughter of his first cousin Nicolò Venier, Lord of Paros. He sold her to the Ottoman Sultan Suleyman the Magnificent in 1536 in order to counter the ascension of Roxelana. She became eventually the wife of his rival Selim II and the mother of Murad III, from whom descend all succeeding Sultans.

Colonna, born at Civita Lavinia, was a member of the famous noble family of the Lazio, then one of the most powerful fief holder of the Papal States and the Kingdom of Sicily (under the rule of Spain).

In 1553 - 1554, during the war against Siena, he was created commander of the Spanish cavalry.

At the Battle of Lepanto (October 7, 1571), his admiral ship was protagonist of the decisive victory of the Christian League against the Ottoman fleet. On his return to Rome, Pope Gregory XIII confirmed him Captain General of the Church.

Marcantonio Colonna was also seignor of Marino, then a village some kilometers south of Rome: the population honored him with a great feast which is held yearly still today, under the name of "Sagra dell'uva".

In 1577 King Philip II named him Viceroy of Sicily.

Queen Paola of Belgium is a descendant of Admiral Colonna on 13th generation. Her great - great - grandfather Fulco Giordano Ruffo di Calabria married Maria Felice Alliata, whose paternal grand - mother is Felice Colonna, a descendant of the admiral and the Lorenzo Onofrio Colonna - Maria Mancini couple.