My husband and I have brown eyes and brown hair, why does our son have blonde hair and blue eyes?

Question

We have 5 children! Four of our children have dark brown eyes: two of them have dark brown hair and the other two have light brown hair. Our youngest son aged 18 months has blonde hair and blue eyes. This has taken us by suprise, because all of our distant relations also have brown eyes and brown/light brown hair, we thought maybe he would only keep it for a short while but it is still there. He is a lovely little boy and we love him very much but we just wonder why he is so different to the rest of us. (Any scientists out there?)

Answer 1

OK, simple version as this gets complicated.

Everyone inherits half their genes from their mum and half from their dad, and this combination of genes is what makes us unique.

Some genes are dominant and some are recessive. The dominant genes will always 'win' over the recessive genes, so if you have one dominant gene for hair colour and one recessive gene, you will only see the influence of the dominant gene (and you won't even know you have a recessive one....unless you start having kids and the genes show up in them!).

Recessive genes are sometimes called 'hidden' genes as their effect is masked by the dominant genes.
Dominant genes usually code for dark features, and recessive for light features (don't know why - this is degree level genetics!)

So, to have blue eyes you need two recessive genes (as one dominant and one recessive gene would still come out looking like brown eyes).
To have blonde hair you need two recessive genes (as one dominant and one recessive gene would still come out looking like brown hair).

Both you and your husband must have one dominant and one recessive gene for eye colour (which, as we learnt before, you can't tell by looking). Your baby inherited the recessive gene from you AND the recessive gene from your husband = blue eyes.
See above for blonde hair!

dominant + dominant = dominant features
dominant + recessive = dominant features
recessive + recessive = recessive features

Looking at the above, you can see that even if you carry one recessive gene AND your husband carries one recessive gene for a certain feature most of your kids will have the dominant (dark) version. However, some of your dark hair/brown eyes kids will be carrying the recessive (hidden) genes, so if they marry someone with the recessive genes, some of your grandchildren could be surprise blonde/blue eyes too!

Answer 2

I would say its just a recessive gene popping up! I'm sure somewhere along the family tree there will be someone with blonde hair and blue eyes.

I know a family that has 4 children, a brunette, a blonde, a light brown and a red head and they have a combination of different eye colours (and no, none of them belong to the milkman!) and the parents are both dark featured people.
My best friends brother is also blonde/blue eyed where as the rest of the family is very dark featured but his face resembles the family entirely. Unfortunately its just the way the cookie crumbles. His hair will probably darken along the way as children very rarely keep blonde hair. My son and daughter were both very blonde but are now a light brown colour. And one has blue eyes and one has brown eyes.

Answer 3

Wow who are you people answering these questions? There's some pretty rude ones out there. racam is right the foundation of mexican history was a mix between the Spaniards and the indigenous populations. I lived in Mexico for 6 years and I had many friends with light skin and blue or green eyes, and some of their parents had very dark skin and brown eyes. Some of these friends even came to visit me in the US during vacation and my american friends were totally amazed that they didn't speak English. In certian parts there are also generations of Mexicans that are decendents from the french, lebanese and germans depending on what part of Mexico you live in. So certianly your husband has the recessive jeans for blonde hair and blue eyes from somewhere in his family history, and you do as well. When taking into consideration all of the groups of people who have ruled or settled at some point in Mexico, it makes perfect sense that this would be so.

Answer 4

Children are often born blond but their hair will darken as they get older. My mum and dad both had dark hair and brown eyes and yet my brother was born with a honey-blonde colour hair and blue eyes. They stayed this way until he was about 18 months - 2 years and then both hair and eyes started to darken. Now at 29 he's black haired and brown eyed, lol!

Me and my partner are both dark haired and brown eyed as well. Our 10 month old son's hair is a golden brown colour (my partner's was the same colour when he was a baby) and his eyes are hazel. I have a feeling both his hair and eyes will get darker over time though.

You may well find your son's eyes and hair will change colour as he gets older.

Answer 5

It's down to genetics.

Blue eyes are a recessive gene so a brown eyed person can carry the gene and not have it show in themselves. Let's call Brown eyed people Bb and blue eyed people bb.

If two brown eyed people have a child, and they both carry a recessive gene for blue eyes it is possible that the child receives both recessive genes. Eg

B b

B BB Bb




b Bb bb

You have a 1 in 4 chance of having a blue eyed baby. The same principal works for blonde hair.

Answer 6

I'm not sure if this will help but this happened in my family. I have 2 cousins, one has dark hair and the other red. Both married women with the same colored hair as they have. When they had kids the red-haired family all had blond children and the dark haired family all had red heads. So genetics play a big part in determining hair and eye color and if it's anywhere in the family it can come out at any time.

Answer 7

Your great great Uncle Richard twice removed on your mothers side may have had blue eyes and blonde hair. The hair colour can change still, it may get darker by the age of 5 (sister in law is a hairdresser). Eyes can also still change up to the age 5. My paediatrician told me. It is still pretty amazing how genes work hey?!

Answer 8

My son also had blond curls and blue eyes at that age, now he has brown straight hair and grey eyes like the rest of the family.

Answer 9

The blonde hair and blue eye genes are recessive genes whereas the dark eye and dark hair genes are dominant genes, this is why most of your children are dark haired. On this occassion the recessive genes just managed to fight there way through giving you a gorgeous blonde blue eyed boy!

Answer 10

I know a family who also has 4 children with dark hair and dark eyes, and they have a little girl who has blonde hair and blue eyes :) It is totally normal