Dec 29 - Another Eye Study

I've been taught in art that the iris of babies is the same size as adults, but it never seemed right to me. So when a friend posted a photo of her family, I decided to do some photoshopping to test it out:

In order, the eyes are hers, her baby's, and her husband's. I haven't adjusted the sizes at all.
Her son's eyes are much smaller than hers (obviously), and even looking at it, it still doesn't totally make sense to me how it works.