I just started a game as the king of Hungary and I noticed I had a 44 year old unmarried sister. I tried to get her married but nobody was listed in the marriage screen, understandable because she has the huge 'past childbearing age' modifier.
I then checked the 'matrilineal marriage' box and suddenly tons of potential grooms appeared, including a young Danish prince! I tried to see why he suddenly accepted and the 'past childbearing age' modifier seems to be gone after checking the 'matrilinear marriage' box.
Is this working as intended? It seems really weird to me that a matrilinear marriage can be more attractive than a regular one for a man.