What's with Twins + Twins?

'... every August, twins from around the globe descend upon Twinsburg, Ohio, for the annual Twins Days Festival. In the past, participants have included twin nuns named Celeste and Celestine, as well as Craig and Mark Sanders and their wives, Darlene and Diane. Craig and Mark are twins, as are Darlene and Diane. They met at the festival four years ago, married, and now live next door to each other in Houston, Texas. Craig and Diane are now the parents of twin boys. If it weren't for the fact that Mark and Darlene have a single daughter, their neighbors would probably think they were seeing double. '

Mary-Kate and Ashley Olsen (a pair of celebrity fraternal twins in the US) might, in the distant future, give birth to twins of their own. If they meet their future husbands at Twins Day, and those men also are twins, then hey--they would be practically giving birth to each other’s children. That’s what happens when identical twins marry identical twins and have children. Their nieces and nephews are, genetically, their own kids.