Casimir III was the last Piast who was king of Poland. Despite having married four times he didn't have any male legitimate heir, and so he arranged for his nephew, Louis I of Hungary, to become the Polish king. Louis ascended to the throne, and also didn't have a male heir, but his daughter Jadwiga married Jogaila of Lithuania, starting the Jagiellon dynasty and the union between both countries.
But WI Casimir had fathered a son, avoiding the reigns of Louis and Jadwiga? How would affect Eastern Europe? And, just to make things a bit more complicated, let's suppose that the hoped male heir of Casimir comes only in 1368, making his last daughter from Jadwiga of Zagan (also named Jadwiga) be born a boy instead. The king dies in 1370, leaving a two-years-old child as his legitimate heir. Who would defend his rights to the throne? And what kind of political mess could happen in Poland during the regency to the child-king?
But WI Casimir had fathered a son, avoiding the reigns of Louis and Jadwiga? How would affect Eastern Europe? And, just to make things a bit more complicated, let's suppose that the hoped male heir of Casimir comes only in 1368, making his last daughter from Jadwiga of Zagan (also named Jadwiga) be born a boy instead. The king dies in 1370, leaving a two-years-old child as his legitimate heir. Who would defend his rights to the throne? And what kind of political mess could happen in Poland during the regency to the child-king?