Actually, what got me thinking about it was a post on GD that had a few picture books about sibling rivalry that a mama said her son found really helpful in relating to a new baby in the family. It got me wondering if there were anything like that related to twins.
Or maybe that's my next writing project?
"Twinkle and Twinette" is an adorable picture book about two twins. Very cute rhymes and pictures. My favorite (and my girl's favorite line)...."Remember to treasure and thank all your stars, that you have a twin who loves who you are!"
I bought mine on Amazon. https://www.createspace.com/4623997
Hope this helps!