Those of you who know me personally know that I have twin girls. When they were born, my OBGYN was 95% sure that they were Fraternal Twins, which means that they are like any other brothers and sister and share 50% of the same DNA. However, as they’ve grown they have maintained the exact same height, weight (only fluctuates between 2-3 oz at any given time), body structure, etc. According to their pediatrician, this is more common among Identical Twins who share 100% of the same DNA, not Fraternal Twins, and he seems to think that they are Identical.

Here’s what’s interesting. When they were about 7 months old, a friend of mine brought it to my attention that there is a third, not so know type of twin called Semi-Identical and they are 75% of the same DNA! This is created by there being one single egg that splits prior to fertilization, and so in turn each identical half is fertilized by a separate sperm (which means there can also be boy/girl combinations of this type of twin). Crazy! I had no idea that the formation of twins was so complex before I found out I was pregnant with twins!

Here are some other fun twin facts I’ve acquired over the past couple of years:

If the babies are in the same sack in the womb, they are definitely identical
If the babies are in two separate sacks in the womb, they can be identical or fraternal (depending on when the egg splits in the case of identical twins).
Semi-Identical twins were relatively recently discovered (they used to believe this was not possible)
Identical twins (very very rarely) can actually by boy-girl combinations also…just saw this on the Discovery Channel! I had NO IDEA!
Identical twins can have slight differences because there are cells floating in the womb after the baby’s initial formation that attach to one or the other twin, creating slight differences among them.
Identical twins can have different birth marks.
Mirrored identical twins have mirrored identical features and often one is right handed while the other is left handed.

Anyway, we are convinced that our girls are Semi-Identical Twins. We think this because we’ve always been able to tell them apart by looking at them…to us they do look different, however, I also know they look a lot alike based on how often I confuse them! Of course we could get a DNA test done to be sure, but it’s more fun to guess.

Here are some very recent pictures of them “acting identical”.
What do you think…are they?