Why is my babies' hair color so different from ours?

Q: My husband has brown hair and I have strawberry blonde hair but my year-old twin boys both have extremely blonde hair... Is this normal?


The short answer is “yes.” But you probably want to know a little more, so here goes! When we learn about genetics in school, most of us study Gregor Mendel’s experiments breeding smooth and wrinkled peas in the 19th century. Since pea wrinkles result from variations in a single gene, this example leads to easy math, as well as a simple understanding of recessive and dominant genes (when an organism has one of each, the dominant gene always wins).
Hair color, however, is a lot more complicated. To start off with, hair color results from the interactions between two different pigments. Eumelanin lends hair its darkness, ranging from platinum blonde to jet black. Pheomelanin makes hair red, on a spectrum from not red at all to Princess Merida in Pixar’s Brave. Further complicating the issue, multiple genes seem to control an individual’s levels of each pigment, and expression of those genes can change as people age.
Since you have strawberry blonde hair, your genes probably code for very little eumelanin and at least some pheomelanin. Your husband’s hair is brown, so his genes code for moderate eumelanin and little to no pheomelanin. That said, genes for darker and not-red hair tend to dominate those for lighter and redder hair, so he could be hiding all sorts of blonde genes in his DNA that happened to be the ones chosen when your sons were conceived.
Remember, however, that hair color can darken over time. Your one-year-old twins are blondes now, but by the time they can drive, they may look a lot like your husband. You can just hope that when your sons do learn to drive, your husband doesn’t pull out all his hair, or you won’t be able to compare.