Another return of Piasts:
Stanisław, Duke of Mazovia, lives long enough to marry Hedwig Jagiellon (daughter of Sigismund the Old), with whom he has posthumous son, whose son in turn marries ATL daughter of Sigismund Augustus. Thus after Sigismund Augustus dies his Piast grandnephew/son-in-law succeedes him.
Stanisław I (1500-1530) Duke of Mazovia, m. Jadwiga Jagiellonka (1513-1573)
1) Stanisław II (1530-1562) Duke of Mazovia 1530, m. Zofia Tarnowska (1534-1570)
Stanisław, Duke of Mazovia, lives long enough to marry Hedwig Jagiellon (daughter of Sigismund the Old), with whom he has posthumous son, whose son in turn marries ATL daughter of Sigismund Augustus. Thus after Sigismund Augustus dies his Piast grandnephew/son-in-law succeedes him.
Stanisław I (1500-1530) Duke of Mazovia, m. Jadwiga Jagiellonka (1513-1573)
1) Stanisław II (1530-1562) Duke of Mazovia 1530, m. Zofia Tarnowska (1534-1570)
1) Konrad IV/I (1553-1593) Duke of Mazovia 1562, Grand Duke of Lithuania, King of Poland 1572, m. Jadwiga Jagiellonka (1554-1607)*
1) Zygmunt (1574-1577)
2) Stanisław III/I (1575-1625) Duke of Mazovia, Grand Duke of Lithuania, King of Poland 1593, m. Maria Christina of Austria (1574-1621)
3) Jadwiga (1577-1584)
4) Zofia (1580)
5) Zygmunt (1582)
6) Konrad V (1583-1604) Duke of Mazovia
7) Katarzyna (1588-1632) m. Albrecht VI (1584-1666) Duke of Bavaria
2) Jadwiga (1555)
3) Zofia (1556-1559)
4) Anna (1558-1601) m. Albrecht Friedrich (1553-1618) Duke of Prussia, has issue
5) Stanisław (1560)
* Daughter of Sigismund Augustus and Catherine of Austria.