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

[Korner]

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!

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

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

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?

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

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

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

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

My dad brown eyes
My mum blue eyes

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

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.

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.

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

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!!

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

Or the milkman’s 😉

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

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

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

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.

I have blue/grey eyes, husband brown, two children with blue/grey, one green/hazel - he is also left handed/footed and to his disgust, I've passed my right footedness to them all! ⚽️ I must have strong genes 🤣

I have green eyes, my DH had blue eyes. Both sets of our parents, blue eyes. But I have native American in my genetic history and have two brown eyed children (plus one blue eyed). They are undoubtedly my DH's. My brown eyed DD has one brown and one blue eyed children. My blue eyed GC has the same unusual blue that my Mother had.

Presumably because none of his family have had children with a person with only blue genes.

My dh is brown his parents brown , green , sibling green , I'm blue as is my parents and sibling. My ds has like green/ Hazel eyes. He's neither one colour or the other. His eyes changed colour quite Late as well around 15 months, up until then they were blue. It's fascinating how it works but genetics in general are fascinating

It's to do with dominant and recessive genes.

There is a certain way you can get each eye colour and some genes are always recessive (can't remember off the top of head as gcse science was decades ago 🤣)

But basically there are percentage chances of each outcome but they aren't dependent (that's more maths and statistics)

So if B = brown (dominant gene) and b = blue (recessive gene)

She could be bb and he could be Bb.

So the outcomes are

bB (brown)
bb (blue)
bB
bb

So basically each child has a 50% chance of blue eyes irrespective what the previous child has.

Or at least that's what I remember from GCSE science!

I'm much more clued up on autosominal dominant gene faults as my son has a genetic condition.

There is so much bad statistics being spouted in this thread ... jesus wept.

My mother has hazel eyes, my dad's are green my sister's are brown and light blue, my brother has dark blue , mine are grey green !

Genetics are funny, my eldest has hazel eyes like me , middle child brown like Dad. Twins have blue eyes like nobody else in the family.