I can't recall seeing anything on this small point of detail - and it may of course be insignificant, but...

Charles Xavier is born on July 5 1915.

Alfin the Vague dies in January 1919.

So why doesn't Charles become king at that time, rather than on Blenda's death? The text suggests that he does not. For example, see the index entries for Blenda and Charles II. Blenda appears to be queen in her own right. The only similar situation I can think of is the joint monarchy of William III and Mary II of England. On William's death Mary continued as queen in her own right, but that was a joint monarchy created in the aftermath of the English revolution of 1688.

Unless VN has created a special Zemblan law of succession for PF, you would surely expect Charles to have succeeded his father as heir apparent, albeit with a regency, on his father's death - the regency presumably enduring until Charles came of age.

But there is a reason why there can't have been a regency on Alfin's death, as Blenda appears to be Queen in her own right and in any event Charles becomes 21 on 5 July 1936, which would terminate the regency - assuming that he came of age at 21. There is no mention of any of this in PF itself.

This may all be rather footling and of no significance, but if anyone can shed light on it, I'd be grateful.