The current PM of Rieleston tried to doe xactly this. Showed up and, like, a month later or somethng, with few messages to the realm, was asserting a right to kingship. That's what led to Rieleston's secession.
Honestly, if Perth tried something like that, my character would pretty much devote his remaining career to stymying it. I just find it so anathema and distasteful in BM to have a clique of players re-creating themselves to secure power.
Yeah, Kerwin argued pretty emphatically about how there is zero precedence for such a thing as the hereditary inheritance of titles (on any level, but especially in the Monarchy), in Eston or BM in general. Because, well, it's true.