As close as many sets of twins are, it's only natural that twins sometimes end up marrying another set of twins. It doesn't happen too often (we've seen one reference to only 250 sets of identical twins married to identical twins in the world) but when it does, it can mean double bliss and a lot of second-glances.The official term for these type of marriages is "quaternary marriages."Read More... More on Anatomical Wonders