As you know, there are two kinds
of twins: identical or one-egg twins,
which have the same heredity, and fraternal or two-egg twins, which have
different heredity. Most of the following
questions are intended to help determine which kind of twins you have. Note: The children are referred to as twins,
even if they are full or half-siblings. Questions relating to sex or gender refer to the natal or biological sex of the child.
In this form, Twin 1 refers to the first born twin, and Twin 2 refers to the second born twin.