Well that worked out (adult now, btw):
The Regent in question died of old age mid battle. I can't punish him, but anyway.
Also, the CB for the king of Norway to claim Kemi ended before he could defeat me (good thing too, since he called in Denmark. I was severely outmatched).
However, right after, half the kingdom rebelled against him, and I "altruistically" offered to support the rebellion. So, new family on the throne of Norway. Yay.
Also, in the middle of all this I managed to wipe out the last family members of the troublesome Svarte family, ruling Gotland. The last heir died childless in my dungeon.
My only problem is that I am chaste, but my brother has excellent stats and a good wife... so come the worst, the dynasty is in good hands.