King of Poland 1506-1548.
Sigismund I was from the Lithuanian ruling House of Jagiellonen, Grand Dukes of Lithuania . After 1386 they also held the crown of Poland, when the last Polish Piast died out. Jogailla or Jagiello was the first one to rule under the name Wladislaw, when he took on Christianity and married Hedwig or Jadwiga, queen of Poland, daughter of Louis I the Great of Hungary . She was the sister of Mary of Hungary , wife of Holy Roman Emperor Sigismund.
Sigismund I was the son of Casimir IV Jagiello and his wife Elisabeth of Austria, who was the mother of the Jagiellonen. The oldest son ruled as Wladislaw II of Hungary and Bohemia.
Sigismund I's mother Elisabeth was a descendend of Holy Roman Emperor Sigismund and of the Habsburgs. A sister of Sigismund's Sophie, born 1464 was married to Frederick V
A younger sister Barbara, born 1478 married George the Bearded Wettin of Saxony.
Sophie and Frederick V Hohenzollern's son was Albrecht, Albert of Brandenburg-Ansbach, later Herzog duke of Prussia untill his death in 1568.
Before Sigismund I became king of Poland, his brothers John I Albert and Alexander had been kings of Poland also.
A daughter of Sigismund I, named Hedwig, born 1513 died 1573, was married to Joachim II Hector Hohenzollern, Imperial Elector of Brandenburg.
Sigismund's son, named Sigismund II Augustus was born in 1520 and became the last Jagiello king of Poland. When he died in 1570/2 , the crown of Poland went with a daughter to her husband John III Vasa, king of Sweden.
The son of Catherine Jagiello and John III Vasa ruled as Sigismund III Vasa of Sweden, king of Poland , king of Sweden , etc.
Sigismund III was married to two Habsburg sisters .