Duchy turning into Principality?

[Galliun]

Problem solved! Somehow managed to get a Catholic heir (not by sending him to a catholic court), and he inherited. Too bad he inherited very old (almost 60), and, to boot, has the plague. Which arrived pretty much as soon as I finished kicking England and Scotland's ass simultaniously (settling for White Peace on both cases - I demolished England, but had no real claims, and Scotland was decimating me on the north, so I like to think it's a win-win for the Irish!).

God, I love this game.

 

[Snaake]

Well as long as you have dynasty members still being born (or that were born before the orthodox stuff) as catholics, and send them to any education than ecclesiastical, you can switch back to catholics in the succession quite easily.

The only times religion is set is when a child is born, and if they complete ecclesiastical education (and if you're a vassal of someone of another religion, an event may fire to convert).