I know of a family like that! Two brothers married two sisters, and each of the couples had like 9 and 11 kids each! They were double cousins. One family was all blonde and fair skinned, the other with more dark features.
I know, I almost married into that family by one of Mary and Herbs kids!
Herb and Pat were brothers and Mary and JoAnn were sisters. Herb married Mary and Pat married JoAnn.