Brought over here from the main thread. I tried searching for this bug on these forums but could not find mention.
I have played 3 games (Roman Republic, Roman Republic, and then Waterford) on Reign of Princes where the starting Patricians of my Republic would not marry at all. I gave one of them a Barony (castle) and POOF he got married immediately.
For some reason, all the AI Republics have their Patricians marry very quickly, with no more than their family house title. I started a Waterford game (Reign of Princes, no submods other than Shattered) and let it run to 1067, watching as Roman Republic had all its Patricians marry and none of mine married. Then I saved game, loaded as Roman Republic, and watched as the Waterford Patricians duly got married within a few months. I reloaded the save back as Waterford and ran the game until 1068 and none of my Patricians got married. My previous Roman games went for decades with families repeatedly dying off. It definitely has something to do with the Player Control of Republics.