In OTL, the Habsburgs continuously ruled the ensemble of the Archduchy of Austria, the Kingdom of Bohemia and the Kingdom of Hungary for about 400 years (1517-1918). And there had been one or two previous Habsburgs who "previewed" that configuration before 1517. This was a really impressive run when compared to other dynasties in the medieval period.
AHC # 1 - Have the Jagiellonians rule this territorial ensemble for an equally long period (or centuries earlier, the Premzylids)
AHC # 2- Have the OTL comparatively brief Luxemburg rule over the territorial ensemble of Hungary, Bohemia and Brandenburg last 400 years
AHC # 3- Have the OTL comparatively brief rule over Brandenburg and Frisia last for 400 years, along with their even lengthier rule of Bavaria and the Palatinate.
AHC # 4- Have any dynasty over the last 1200 years control this territorial configuration, "(almost) from Stettin in the Baltic to Trieste in the Adriatic" for at least 300 years.
illustration below: