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Original poster

Can someone explain chances of 4 kids with blue eyes when one parent is brown eyed?

142 replies

Korner · 30/05/2024 19:38

Dsister (blue eyes) has 4 kids with BIL (very dark brown eyes almost black). All 4 kids (7 - 3 yo) have bright blue eyes.

BIL is Sikh Punjabi. Apparently has no history of blue eyes but says some second cousins have green eyes - not common but not unusual. My family all pretty much have blue eyes.

This has to be an anomaly. Just curious as the discussion came up at baby group today. Learned that it should only really be 50% likelihood of blue eyes if one parent has brown eyes and the other
blue.

I have one of each (brown and blue) despite DH being green eyed. I’m also blue eyed.
Genes are very interesting!

OP posts:
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7
hellsbells99 · 30/05/2024 20:30

I have brown eyes and both of my DDs have blue eyes. One also has blonde hair when both DH and I have brown hair.

Katemax82 · 30/05/2024 20:30

My husband had 5 kids in total, me and his ex have brown eyes, his are green. 3 of his kids have green eyes

Namechange43654 · 30/05/2024 20:28

LateMumma · 30/05/2024 19:55

Can two parents with blue eyes have a brown eyed child then?

That is rarer, but it's still not impossible.

TheYearOfSmallThings · 30/05/2024 20:28

Korner · 30/05/2024 20:15

So the fact that BIL says no one in his family have blue eyes is because brown is dominant?

Why has there been no other expression of blue on BILs family if he has the blue gene?

Edited

Most likely because his family members have not been marrying blue eyed spouses.

saltinesandcoffeecups · 30/05/2024 20:27

It’s down to the recessive genes in your BIL’s family.

Or the milkman’s 😉

inquisitiveinga · 30/05/2024 20:26

I have 2 bright blue eyed children and I myself have incredibly dark features with heritage from the Middle East/South Asia. Dad has blue eyes... all that work that neither of them resemble me in the slightest!!

MrsSkylerWhite · 30/05/2024 20:24

Our daughter and her husband have brown eyes, his verging on black. Our grandchild’s eyes are cornflower, like his grandpa.

MargaretThursday · 30/05/2024 20:24

It's not quite this simple but on a very basic level:

So if they have one or two brown eyed genes they have brown eyes. Only if they have two blue eyed genes then they have blue eyes.

She has bb (2x blue eye genes), call them b1b2
He has Bb (1 brown, 1 blue) call them B bx
So any child they have can be
Bb1 or Bb2 and have brown eyes
bxb1 or bxb2 and have blue eyes.

So each child has a 50/50 chance or 1 in 2 chance of having blue eyes.

If they have 4 blue eyed children the chances of that is 1/2 x 1/2 x 1/2 x 1/2 =1/16
ie For every 16 couples with the same genes, one will have 4 blue eyed children (and one will have 4 brown eyed children by the same calculations)

So not as uncommon as all that.

However eye colour isn't quite as simple as that, but I don't know enough to go into it. Dh's cousin has brown eyes and both her parents (and, yes they are definitely her parents) have blue eyes.

ShortColdandGrey · 30/05/2024 20:23

I have green eyes and dark brown/black hair. My husband has brown hair and brown eyes. We have a blonde haired and blue eyed daughter.

SapphireSlippers · 30/05/2024 20:23

My dad brown eyes
My mum blue eyes

Eldest blue eyes
2nd brown eyes
3rd blue eyes
4th blue eyes

PuttingDownRoots · 30/05/2024 20:23

I'm brown eyes, my parents and brother all blue eyed. My biology teacher hated me! (Not really).

saltinesandcoffeecups · 30/05/2024 20:22

Here are the possibilities:

  • Blue eyes + blue eyes = 100% chance of blue eyes.
  • Brown eyes + blue eyes = 50% chance of blue eyes, but only if the brown-eyed parent carries a blue-eyed gene. If not, the chance is 0%.
  • Brown eyes + brown eyes = 25%, but only if both parents carry the blue-eyed gene. If not, the chance is 0%.

It is important to remember that this theory is a simplified version of what really happens at the genetic level. Human eye coloring is actually controlled by a complex genetic process and there are many different eye colors other than just blue eyes and brown eyes.

https://www.familyeducation.com/babies/growth-development/what-are-the-chances-my-baby-will-have-blue-eyes-a-genetic-explanation

Can someone explain chances of 4 kids with blue eyes when one parent is brown eyed?
Moreorlessmentallystable · 30/05/2024 20:20

Both our kids are blue eyed, coming from 1 parent with blue and 1 parent with brown eyes

FairFuming · 30/05/2024 20:15

My dad has brown eyes and all 3 of us and his 4 GC have blue

Original poster
Korner · 30/05/2024 20:15

So the fact that BIL says no one in his family have blue eyes is because brown is dominant?

Why has there been no other expression of blue on BILs family if he has the blue gene?

OP posts:
Nottherealslimshady · 30/05/2024 20:13

50% chance for each child. The same as sex. It's literally no different to a couple having four sons .

Beezknees · 30/05/2024 20:11

It's the opposite for us, I have greeny blue eyes, my ex has hazel eyes, and DS has dark brown eyes.

Aworldofmyown · 30/05/2024 20:10

My parents are green and blue eyed. I'm brown!!
Dh has brown, our kids are brown, brown and green eyed!!
It's much more complex than people think.

Mnetcurious · 30/05/2024 20:10

You could toss a coin 50 times and it might be heads every time. Statistically it’s more likely to be heads only half the time but it’s not impossible for it to be heads every time.

Lemonade2011 · 30/05/2024 20:06

I have 4 children, my eldest is red haired and brown eyed and my second is blue eyed and blonde, I have green eyes his dad has brown. My youngest 2 3rd is blue eyed and dark hair 4 th dark curly hair and brown eyes their dad was dark haired (bald now) and blue eyes. So a bit of a mix up my bil insinuated that my youngest wasn’t his dads due to his dark eyes. 👀

IggyAce · 30/05/2024 20:06

I have dark blue eyes and my Dh chocolate brown, ds had the same colour as dh. DD eyes are an amazing mix golden/hazel/grey they used to change colour from one day to the next.

SonicTheHodgeheg · 30/05/2024 20:06

My ex and I have brown eyes.

Our children’s eyes are brown, blue and green which has taught me that genetics is a lot more complicated than I thought.

We both have a blue eyed parent so I assume that the grandparent’s genes played a part here.

EternalSunshine19 · 30/05/2024 20:03

My cousin is mixed race with green eyes and has a 1 year old with blue eyes. The babies' mother is mixed race and has brown eyes, but her mother has blue eyes. Its a recessive gene

FTPM1980 · 30/05/2024 20:02

Korner · 30/05/2024 19:53

So what does it mean when some posters are saying there is more than one gene at play? Sorry dropped Science after GCSEs!

I don't know the full detail but genes carry the code for making the pigment(s) that give your eyes their colour.
So you could have a gene at place 1 that codes for brown pigment, and you can either have 0, 1 or 2 copies of that.
But another gene at location 2 could also make brown.
And then another at locations 3 could make more of a green.....combined with no brown would give bright green, combined with brown would give Hazel.
Other genes can also switch the genes for eye colour on and off which plays a part.