So, I realize that this question has probably been asked several times before, but here we go again. Sigismund II was the last king of the Jagiellon dynasty in Poland. He seems to have had a low sperm-count, since after three marriages he died with no children (although his third wife had suffered a miscarriage in 1554 and there is mention of a bastard daughter, Barbara (who died in 1615) in some sources). How does Sigismund act following the birth of an heir to either Barbara Radziwill (1548-1551) or Catherine of Austria (1553-1572).
How does this change the dynamic of the Polish-Lithuanian monarchy? Sigismunds I and II seem to have been rather wily old jackals when it came to politics, and Bona Sforza didn't lag far behind, so what might we see happen? Poland move closer towards absolute monarchy a la the rest of Europe?