[muawiyah]

The answer is that they were not related within four degrees of consanguinity.

That's been pretty much the rule since "the Family" was founded way back when by Hugh Capet.

ALL of these people are multiply descended from French royalty ~ even the commoners.

Not that it's a "rule" but it's kind of hard to escape the problem.

[Guenevere]

Are you sure?....Queen Victoria’s mother’s brother was father to Prince Albert.