So this is weird. I've had gravelkind all game (which I started before 1.06b), but my 2nd, 3rd, and 4th kings all had at least one kingdom upon their deaths. I've always had the eldest son inherit everything but a duchy and a few counties. My current guy and his father (6th and 5th kings respectively) both have/had one son, so I can't really test if it's fixed right now. Could it just be that I'm Irish?