It is passed through the X chromosome, but it is possible that it was passed from further up the lineage through a mother or grandmother somewhere.
Plus, not all fraternal twins are a result of genetic inheritance, some are just plain luck or diet. For example, some types of yam have a tendency to make women release multiple eggs during ovulation. Also, women who consume a lot of dairy, have children late in life or are overweight may release multiple eggs to increase the chances of having twins.
Genetics is only part of it.
As for your names -
Theresa Niamh is adorable and classy at the same time! I like it with
Charlotte a lot.
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"How wonderful it is that no one need wait a single moment before starting to improve upon the world." -Ann FrankMama to my "bright star"
Clarisse Bituin and Wife to
Julius.
Mahal na mahal from our little family to yours!