Constantine was educated first at the Imperial Galatan College and later at the Pandidakterion, where he studied for a degree in biology. He later studied for a PhD in exobiology at Queens' College, Cambridge, where he was a keen rower and was even part of the men's coxless four team for the Roman Empire at the 1972 Summer Olympics. In 1974 Constantine married a commoner, Zoe Demetriadina, in Constantinople, a marriage that caused much controversy at the time. The couple have two children: Theodora, Despoina of Epirus (born 1976), and Prophiphoros, Praetorian Prefect of Syria (born 1979).