Enrico Dandolo was a Venetian nobleman who later was elected Doge. Born in 1107, he spent most of his life on diplomatic missions. In 1171, at the age of 64 he accompanied Doge Vitale Michiel on a retaliatory military campaign against Constantinople which proved to be a disaster. He survived a plague epidemic and returned back to Venice only to be appointed an ambassador to the city a year later.
Around this time Enrico started losing his eyesight, as a result of a head wound which he presumably acquired when he was attacked by the mob in the streets of Constantinople though there is little information on the exact circumstances of his injury. By 1176 he appears to have been legally blind which didn't prevent him from fulfilling his duties. In fact, in the following years he twice travelled to Sicily as an ambassador to the King and went back to the city which he hated in 1183, to negotiate the restoration of the rights of the Venetians.
In 1192, when he was 85, Enrico became the next Doge. Despite his age, he was still very ambitious. In 1194 he undertook the currency reform which made Venetian money the dominant currency in the region for the coming years but that was not all. 10 years after his election, when Dandolo was 95 (yes, you read it correct), he decided it was time to go to war and thus took part in the fourth Crusade which sacked Constantinople so that he finally could pay back for all his humiliations.On the way to the city crusaders also sacked the Hungarian town of Zadar simply because they could which led to their excommunication but Enrico didn't seem to care.
Constantinople fell in 1204, and Dandolo played the leading role in this event. As a result, Venice gained the rights to 3/8 of the Byzantine Empire and one would think that at the ripe old age of 97 it would be enough for Enrico, but he apparently just tasted victory and wanted more so he went to fight against the Bulgarians. The crusaders lost that battle and Enrico died 3 weeks later, probably from disappointment, at about 98 years of age.
His son Raniero survived him only by 4 years since he was killed in battle in 1209 but his granddaughter Anna married into European royalty and became the Queen of Serbia. It's unclear whether Enrico had other children besides Raniero, but it's certain that he was married while being a Doge, probably to a much younger woman whose name was Contessa. Raniero appears to have been his son from his first marriage because he apparently already had children of his own at that time and even served as vice-doge during his father's absence.
You can read more about this remarkable man over here.