Question

Why don't identical twins always have the same mental or physical conditions?

Answer 1

Identical twins have same genetic makeup. Physical conditions may be different, because its is expression of genes.

Explanation:

Identical twins have same genetic makeup. This is called as nature of the twin.
Nurture is conditions under which the twins develop. Lot of research is done on separated identical twins in early childhood.
They may not have same physical and mental abilities.
Nature and nurture develop the baby.