The short answer is "no". Identical twins are genetically identical, but genetics count for only part of how we are. There are so many variables within individual chemical balances and environmental elements that identical twins, though they look the same, are often no more alike than other siblings. There are plenty of examples of id. twins being genetically predisposed to something (short sightedness for example) but not suffering to the same extent.

Nature and nurture are both very important and it's likely there are things we haven't even thought of which make a difference.

Bx