Update: Shem up and went crazy and got himself splatted. No heir. Asmel went crazy and starved herself to death. She has a heir who is now the countess. My original baron went crazy and went all berserk on his fellow dwarves. He died. No heirs. So I'm down to two without even having to plot their demise!
And then I got a Forest Titan who spat webs and found a sneaky way into my fortress and killed everyone. Oops. Next time: better military.
Clearly when you make a nice tavern and chapel every fucker in the whole world hears about it -- about a third of my population now are entertainers and pilgrims who decided to stay and apply for citizenship.