Which is the largest twin brother?

What is it? The first born? Does the first in shape?
Much has been said about that first birth is the lowest and the highest last. None of that is true. For the law, the first born, is undoubtedly the largest. Simple question of logic. In biology, everything is possible.

In the case of identical twins, generated from a single fertilized egg, both biologically-be-equal in age, and that his life began simultaneously.

If these are simple twins, the product of fertilization of two different eggs by two different sperm, there is-to-date any possibility of knowing if the fertilization was simultaneous or deferred.

And in the case of in vitro fertilization?
Even if, as in the case particularísimo of in vitro fertilization, we know exactly the time at which each egg was inseminated and the time at which each embryo was transferred to the interior of the uterus, we will never know which is which at the time of birth. That figure could only be made known whether a biopsy for genetic study of the embryo before transferring to the uterus, something-for now-is only possible in very limited. Most countries where technically feasible, the laws are very strict regarding the possibility of the so-called "pre-implantational biopsy of embryos.

Almost science fiction. Hence, not to discuss more: the first birth is the largest, but in reality was the ultimate gesture.