Paul,
I noticed in my tree that several cousins inter-married, BUT only had children if they were three generations between their common ancestor. My family was obsessed in keeping their wealth. At least, up until about WW1!
I remember from reading a book about Eleanor of Acquitaine that there was a catholic rule, that could only be overuled by papal intervention, that stipulated this.
What are the exact genetic effects upon say immunity?
I know they quote Queen Victoria and the general Sax-Coburg line and their genetic diseases as the most common example.
Geoff.