Yes that's totally possible. And honestly I was a little disappointed no one seemed to be interested in that quest line. So I'd be thrilled to let you run with that angle. We should give your character a trinket of some sort connecting them to the throne. Like a broken locket or a birthmark. 

I will say I'm not crazy about the idea of your paladin not having any faith affiliation whatsoever. At the very least I think I'm would want to see a strong and clearly defined moral code your character swears to uphold. In addition, I think it would be very helpful if your character at least had some soft opinions about the three major faiths in this setting (The Sacred Flame, The Falling Fire, and the Old Gods). I'm more than happy to give you info on those things or answer any questions you might have to help you get these details settled.  

If you're interested here's a link to the "Oath of Hexes" subclass for paladins created for the Drakkenheim campaign...
[url]https://www.worldanvil.com/w/drakkenheim-stevensummers96/a/paladins-of-drakkenheim3A-oath-of-hexes-article[/url]