Uncle Leo
This cook is an anti-semite
Though the book Your Genes Unzipped: A Guide to How Your Genetic Inheritance Can Shape Your Life Tim Spector , they explain that twins are among the best used as social influences are lesser and they are essentially clones (which gentics wise they are ).
Only identical ones, i.e. those that have come from a split egg. I've changed two different babies this morning and can confirm that my twins aren't identical!
Touching on what you say though (albeit slightly off topic) I'm fascinated by how my two will grow up alongside eachother. Boy and girl, possibly very different characters, but living pretty much in eachother's pockets for the first years of their lives. As those on here who knew my Dad and uncle will be able to testify, even identical ones can have a difference or 12.