The second good question is about non-English royal lines. I used to subscribe to the notion that finding gateway ancestors was purely a British anomaly. The conventional wisdom was (is?) that due to the practice of primogeniture in England, whereby the eldest son inherited everything and other sons, nothing, you had a sort of downward mobility which allowed for such connections. Younger sons of kings became nobles; younger sons of nobles became the landed gentry; younger sons of the gentry became professionals, and these professionals or their sons came to New England where they could own property. The question is: is this a canard? Something we were taught, but when one actually examines it, is it true? I don't know.
I do know this discussion is happening at soc.genealogy.medieval and has been for over a year. I know that Gary Boyd Roberts will finally include French Canadian royal lines for the first time in the 2010 edition of Royal Descendants of 600 Immigrants to North America (North America heretofore meaning the 13 original colonies). No word on Hispanic lines. I know there are some Scandinavian lines now. However, as a rule, are continental royal lines provable? Again, I don't know. The continental lines seem to be solely found via (at least one) illegitimate birth. Overcoming that proof problem can be difficult. Then there is language. And are the continental nobility registers as good and complete as, say, Burke's Peerage?
My royal lines are from just three of my eight great-grandparents. I always assumed that my Scottish-born great-grandmother would also have at least one, if I did the work. This may be true, but since the records for the lowest classes of Scotland cease in the early 18th century, I can't make the leap to 16th or 17th centuries to find such a noble family. Likewise, my Slovak ancestors were, more or less, peasant farmers. They were Lutheran in almost all lines so far as I can tell, and therefore, the records are spotty for them pre 1770. Maria Theresa allows freedom of religion in 1772 (enlightened despot she), but before that only Catholic registers remain. My ancestors simply don't appear in them. Could one of them descend from an illegitimate birth? Possibly, even probably, but how to prove it and when?
So, perhaps others will get interested in medieval genealogy and the fact that noble and royal genealogy is the only reliable way to do that [even in England, the average person of non-noble birth can't be traced before 1450 as a best case scenario]. That will lead to more gateway ancestors and more discussions of what sources there are out there.