> Andrew's family rules Britain (for what, 1200 years? [1]),

Try a bit over 100. The House of Windsor ascended to the throne of the United Kingdom in the misty past of … 1901. Even if we disregard royal houses and look at just successions then you run into some awkward situations pretty early, including a nice run of kings born in Hanover and speaking primarily German.

A lot of royalist propaganda is an attempt to tie relatively short lived dynasties into some mythical long lived chain of succession, mostly to reinforce the idea that they rule by right rather than by force or accident of history. In reality royal houses are regularly discarded when they become too inept, too inbred, or (in England’s case) too Catholic for the people to tolerate.