Gustav was a Swedish prince, the son of Eric XIV and Karin Månsdotter.
Background
The infant Gustav was present at his mother"s wedding to the King of Sweden in 1568 and at her coronation, together with his sister Sigrid. After his father"s dethronement, Gustav was sent to live outside of Sweden in 1575, to protect him from King John III who feared that the supporters of Eric would try to deprive his son of the crown.
Career
Gustav came to Poland where he lived in poverty and despair. At some time during his stay he became a Catholic. Ivan IV of Russia attempted to persuade Gustav to help him in his political ambitions around the Baltic, but these attempts (which included both promises and several years exile) failed.
In August 1599 Gustav arrived in Moscow for a proposed marriage to the Tsar Boris Godunov"s daughter Ksenia.
But there, he lived a self-indulgent life. After the death of the False Dmitry, the new tsar, Vasili IV of Russia, released Gustav and sent him to live in the small city of Kashin, Russia.
Gustav Eriksson Vasa died in February 1607 in Kashin and was buried there February 22. He was in elder history writing thought to have had four children with a certain Brita Karth and perhaps even have married her.
This has however been refuted by modern historians.
Gustav is the main character of the famous Polish novel "Broken star" by Jadwiga Żylińska.