As a professional genealogist in London for 30 years, I used to run into the problem of people not being too happy about the amount of recent illegitimacy within a lot of people who came to me hoping for traces of blue blood.
I could warn you that it is almost certain to be much higher in the United States and anyone seeking a position in the former BLUE BOOK, should not attempt this endeavour in order to find out you are willing to accept having had unwed relatives in your family tree.
It has lead to nervous breakdowns and suicide among aristocrats and particularly Americans who speak of rumors of their ancestry having been grand.