Looking through the thread about Crusader Kings on a CK Reddit, I ran into the following throwaway comment:
The genocides, the murders, the marrying your grandmother and having kids........beautiful!
I know we discussed other weird marriages in this game here (" Is marrying my own sister a good idea?Is marrying my own sister a good idea? "), but can the game actually be practically played in a way that you can marry your grandmother and have kids? How?