WOW, did you already know all that or did you do a quick Google search???
("always verify your references").
The trick, of course, is knowing where to look.
I am a bit of a bug on British royal genealogy, so I have a couple of websites on tap. I'm pretty solid on the British royals without having to check, but when I get off into collaterals like the Oldenburgs, I have to go look.
And once you get into Queen Victoria's era, they are so intermarried that the Guelphs and the Oldenburgs and their various collaterals keep crossing generational paths.