Apparently “identical” twins don’t even have identical genetics:
Identical twins emerge when a zygote — the fertilized egg that develops into an embryo — splits into two embryos. As such, they should have the same genomes. The researchers speculate that as the cells making up each embryo divide over and over again during development in the womb, mistakes occur as dividing cells shuffle copies of their DNA into daughter cells.
But genetic differences between identical twins might also accumulate after development over a twin’s life as well. “I think all our genomes are under constant change,” Bruder told LiveScience.
I think that this has implications for cloning as well. It may not be possible to exactly clone an individual, and the differences could turn out to be quite noticeable.
[Update in the evening]
Per some comments, the key point in this story is that it has long been known that there are differences in twins (personality, eyesight, fingerprints, etc.). But those are things that can arise even from an identical genome. The genes are not a blueprint, but rather a recipe, and even if a recipe is followed carefully, the results are not always guaranteed to be the same. The point of the article is that, contrary to previous theories that obvious differences in twins could be attributed solely to different environments, that the genome itself wasn’t necessarily the same. That is new.