Siemowit was a relatively skilled politician and a candidate for Polish throne after the death of Ludwik Andewagen (Anjou) in 1382. What if manages to marry Jadwiga and secure Polish throne for himself?
Some random thoughts, as a basis for further discussion:
- Most far reaching consequence is no Polish-Lithuanian union. Instead only a short-term military alliance against the Teutonic Order.
- What happens to Lithuania? Who and when Christianizes Lithuania? Lithuania still has some potential and had it focused exclusively on eastern politics it might gather enough Russian lands to counter the eventual expansion of Muscovy. Or would it succumb to triple pressure of Teutons, Muscovy and Tatars?
- What happens to Poland? Without Lithuania it becomes relatively small in terms of territory (no Wolhynia, no Podolia, no Ruthenia, ect.) and thus much less emphasis is put on eastern politics. Will szlachta still gain their privileges?
- Teutonic Knights defeat is exploited earlier and more completely, as there is no need to preserve common Polish-Lithuanian enemy to help unite those two states (as arguably was the case with Jagiellonian dynasty)