Yes, once again, I end up thinking about monarchy- not necessarily how it is or how it was, but how it could be. See, a monarch's family is a bit of target; there are plenty of people who either want to marry into it or want one of their descendants to marry into it. This can be a good thing, and our descendants could eventually have the sort of unity that our misguided contemporaries like to proclaim, usually while living in the whitest of white places, like Oregon or Connecticut.
This only has meaningful social value with a solid marriage culture and actual standards. Actually valuing intelligence, for example, would go a long way in nudging the long term trends in the right direction. Standards are meant, of course, to encourage people to take a long term view, marry smart people, and concern themselves with the education and morals of their children. We should come by unity honestly, and with the added strength of improving ourselves both intra and inter-generationally.
Such a royal family would grow somewhat large, given time. It's not healthy to have all these smart people sitting around, so we'd have to give them something to do. How about doing, peacefully, the exact opposite of what Bismarck did to Germany? Encourage smaller and smaller governments over the generations. Competition is good!
Naturally, people gravitate toward the great nation-state idea, but much of that can be dealt with psychologically, or symbolically. Perhaps education will work, in which case, we wouldn't have to worry about it at all.
Several generations later, they are basically just local judges, competing with each other for business, and/or eschewing their 'royal obligations' for more interesting work in private enterprise.