Why Cousins, Unca's and such...?

[Darin Reid]

    Anyone have any idea why the Ducks (and even the mice) never seem
to be directly related?  It seems like everyone is an uncle, an aunt,
a cousin or a grandma.  Was there some strange Disney unwritten law
saying that parenthood wouldn't be discussed (That definitely does not
hold today - Goofy has a kid!)?  Or, was this a decision made on the
part of either CB or FG?