[quote=@Peik]
Why not just make the claimant unrelated blood-wise, like a vizier, or influential count? It's always nice to have grey and grey. 
[/quote]

In that cause they'd need a good reason to want to rule, aside from power of course. I was thinking of something tragic for the claimant, such as witnessing their father being murdered/assassinated and mother raped. Thus paving a way for your basic heroes journey... 

Of course there is the risk said person would end up being more interesting than our characters. :P