Board Thread:Speculation House/@comment-165.234.188.171-20151017013825/@comment-4010415-20151017022918

Yeah, basically, "twin" just means they developed and were born at the same time. Twins can be created in different ways, with differing results.

Identical twins - The whole reason they're identical is because they came from the same egg. The egg split into two different embryos.

An egg carries half the genetic makeup of a person, and a sperm carries the other half. It is the combination of the mother's contribution (the egg) and the father's contribution (the sperm) that determines what the child will look like. Identical twins coming from the same egg fertilized by one sperm is what leads to the twins looking identical. They got the same genes.

Fraternal twins, where two eggs were fertilized at the same time by the same father, look different because the eggs have different genes.

What genes a child inherits from either parent is entirely a gamble.