I like this and think it has value. In the UK there is not an evening goes past without a TV programme on the royals. There's loads of eccentricity in the Windsors, Stuarts, Tudors etc and therefore loads of freely available info out there to publish. An easy blogging subject. The real aristocracy in UK and Europe are/were totally mad, and therefore interesting. The new ones that married in can be good looking; Di, Pippa, Kate.
You could blog a big family tree and use that as the index with links to individual posts and pages.
Monetising would be a challenge, as I can't think what adsense would dispkay, or what you could sell on it. Trinkets, mugs etc might be possible.
The money might be in building a basic blog then offloading for <$500. You could be lucky and get some old money from a real aristo!
Domain on its own <$50 perhaps, but as I say, you might get lucky.
Just some thoughts.