Olaf II of Denmark

Born in December 1370, Olaf Hákonsson came to the Danish throne in 1376 as Oluf II, his claim running through his mother's royal blood. Four years later, in 1380, his father Haakon VI of Norway died, and the boy inherited that crown too, reigning there as Ólafr IV. For seven years he held both kingdoms in personal union, a rare double monarchy in medieval Scandinavia. On 3 August 1387, still only sixteen, he died. The thrones passed to his mother, who would forge them into the Kalmar Union.