What is the term used to describe the relationship of the children of
two families where both fathers are brothers and both mothers are
sisters?

Dear djc1380,

I found your question to be quite intriguing. The answer is that the
cousins you describe are known as "double first cousins", or sometimes
just as "double cousins".

An overview of less common cousin relationships can be found at on
genealogy.com, at:
http://www.genealogy.com/heard122800.html?Welcome=1028779582

Another interesting page from CousinCouples.com provides an overview
of state laws regulating the marriage of cousins:
http://www.cousincouples.com/info/states.shtml


Search Strategy:

A Google search for "fathers are brothers" "mothers are sisters"
://www.google.com/search?q=%22fathers+are+brothers%22+%22mothers+are+sisters%22


Thank you for the opportunity to answer such an interesting question.

- expertlaw

While seemingly a simple answer, I appreciate the great service and in
particular the terrific links and suggestions for enhancing my
research projects.