Just a cursory glance at the marriage dates of Zygmunt I, king of Poland's daughters shows that only the two eldest daughters were married by the time of their dad's death - and they were the only two who had married at remotely reasonable ages (Hedwig at age 22, and Isabella at age 20). Naturally Zygmunt's death lowered the marriage opportunities of his remaining daughters, Sofia, Anna and Katarzyna - who married at 34, 52 and 36 respectively.
Why was it that those girls weren't married off during Zygmunt's lifetime - in 1548 they would've been 26 (Sofia), 25 (Anna), and 22 (Katarzyna) (already older for the European marriage market, but not too old). Or was it much like Louis XV's daughters - simply not enough surviving princes on the market to offset the princesses? And what would the earlier marriages of those Polish princesses mean for the future of the PLC?