AI won't honor Matrilineal betrothal.... unless I let THEM suggest it.

[Meneth]

That's just because the AI sends the request before you hit the button, and then by the time it reacts to your response the marriage has already happened because you agreed to their proposal, so the game correctly determines that marrying those characters again is impossible and sends a negative response. You used to get similar stuff back when there would temporarily be no regent when you loaded the game as an underage character, and then you could send diplomatic requests that would normally have to be approved by the regent. Then you would unpause the game, you would get a regent assigned, and the AI would decline your offer because it was now being blocked by the regent.

This and the original issue are both fixed in 2.8. Not 100% sure about the original issue, but the one you mention definitely is.

 

[Meneth]

Does this mean we can no longer matrimarry heirs and landed characters by just waiting for the AI to make a proposal to honor a betrothal? Or that the AI will now break betrothals when the marriage becomes unacceptable?

I think we changed it so they honor the betrothal, but I'm not 100% sure.