how can two blue eyed parents have kids with brown eyes?

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My parents both have blue eyes and my siblings and I all have brown eyes.

In: 5

Are you *sure* they are both your birthparents?

Naw, it’s definitely possible. Eye color is a complex trait that probably depends on several pairs of genes. We don’t really understand how it works at the genetic level yet, but we do know many blue eyed parents have brown eyed kids.

Eye color is not an example of a simple genetic trait, and blue eyes are not determined by a recessive allele at one gene. Instead, eye color is determined by variation at several different genes and the interactions between them, and this makes it possible for two blue-eyed parents to have brown-eyed children.

https://udel.edu/~mcdonald/mytheyecolor.html

One of the misconceptions here is how genetics is taught in early education. There seems to be an emphasis that because blue eyes are recessive, and you have both parents with the recessive gene, that they can only pass on the recessive gene, but this isn’t how it actually works.

Think of genes as a bowl of colored M&Ms. Your parents have a bowl each, and you will make your own bowl by grabbing a handful of candies from each of their bowls. Now your parents both have blue eyes, so a large majority of their M&Ms are blue, but because of their ancestry, they still have a lot of brown candies in the bowl.

So you come along, scoop out some candies from both parents, and as fortune has it, you just happened to grab a bunch of brown candies in each hand, even though chances were much better that you would have grabbed a majority of blue candies. Now, you will still probably also have grabbed some blue candies, and probably much much more than if your parents both had brown eyes; but, because you have so many more brown candies than blue, you have brown eyes.

This means that your kids will most likely have brown eyes, but still have a very good chance of having blue eyes (depending on their other parent’s contribution.)

Hopefully I made that simple enough without making it too inaccurate…

If you look closely at eyes, there may be more than one color. If both of your parents are pure blue eyed without brown appearing pigment close to the iris with a fanning of blue (sometimes referred to as hazel eyes) it is unlikely that your father is biological. Two pure blue eyed parents will not have 3 brown eyed offspring naturally despite what many of the other commenters have said above. If however one or both of your parents eyes are hazel, the probability increases. Yes, the genetics are more complicated than bb bb vs Bb Bb punnet squares however the probability of two light eyed parents having 3 dark eyed offspring is very rare.