I think you are missing the real matter. Surely in all the centuries of the
empire there were be brothers and sisters of the emperor, problably each
emperor had some sisters or brothers. Each of them found a line deriving
straightly from that of Roele. The point is that this is only an official,
bureucratic matter. The wise Dosiere family now that it will not be enough
to have a lord of Roele's line, but it must be an unsurpassed lord, he must
have all the real characteristic that make difference between a man and an
emperor. So there will surely be a lot of right pretender, but the
Chamberlain is waiting for the right one, that with, we can presume, the
bloodline powers of the Roele. Not only with the right line. It is more
realistic that the Dosiere Chamberlain will give the trhone to a man that
proved to have the great, enourmus mana resources needed, even if not from
the Roele line, nor that he will give it to a discendent who has done
nothing real important.
And when I mean real important I mean something like fight the Gorgon, or
the Spider or the Manslaughter. Or something else like conquering the favor
of most Anuirean regent. Something, everyway, real unique!

Nadastor, Wizard of the Black Robes
"The power of a man is not in his hands, but in his eyes !
His life is not into his body, but into his mind !
The world is not around him, but is in him !"