Mutant Genes:

Red hair and brown eyes is unusual. Red hair is a recessive trait but brown eyes tend to be dominate. Hair color and eye color are one the same gene, MC1R. So if you have a dominate hair color you tend to have a dominate eye color, brown hair and brown eyes for example. People who have red hair and brown eyes have a mutated gene so the recessive red hair is attached to the dominate brown eyes.

The same concept goes the other way, like people with green eyes and brown hair.

Lots of people in my family have red hair/brown eyes because of this. It doesn’t skip around like it does in some families.

My wife has brown hair, brown eyes and an olive skin complexion. I’m your typical scandi with reddish-blonde hair, blue eyes, skin that burns like paper. Our child has brown eyes, red hair and olive skin that actually tans. It’s bizarre.

Can I ask what color your kid’s freckles are? I ask, because the redheads in my family have orange freckles, and the non-redheads have brown freckles. It looks like that correlates with the type of melanin, which would also affect whether they tan.