John, Prince of Schleswig-Holstein

Johan of Schleswig-Holstein was the youngest son of Frederick II of Denmark and Norway and Sophia of Mecklenburg-Schwerin. He went to Russia in 1602 as the bridegroom of Boris Godunov's daughter Ksenia (Xenia), but fell ill and died before the marriage could take place. John's death is unknown. It is possible that Boris Godunov's ministers may have poisoned him. The cancelled marriage between John and Ksenia was a attempt to ally Denmark with the Russian Empire. If that would have happened and if John had lived and had issue history might have gone in a different direction.