Eddis, Attolia, Sounis

Nicely put. Plus a single queen is a risk to the country's stability because there's no direct line of succession. If the queen dies without a direct heir, there could be a civil war over the throne. (This was a big concern in England when Elizabeth I took the throne.) If that uncertainty is removed, however, a baron has less to gain by scheming against her - he can't take the throne, nor can an ally. And since he needn't fear one of his enemies taking the throne, he can relax.