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!

Me and my dh have dark brown eyes. Our first born has green eyes. No one in our family has this colour that we know of. Beautiful though.

You have to make a venn diagram

I am half Indian with brown eyes and black hair. My DH is English with brown hair and blue eyes. Our children are both blue eyes with fair hair.
My sister has blue eyes. Father Indian and mother English.

Very interesting to learn about.

Funnily enough when we were in Greece with BIL and sister last year people kept speaking to BIL in Greek!

Genes truly are fascinating.

I used to live in Brazil. Many people there have a stunning combination of dark skin & hair with light eyes. It's usually explained by Brazil's genetic 'melting pot' which, going back 150 years, would have included European men having children with African women. This would mainly have been enslaved women, but the Portuguese government did pay settlers to marry local women - meaning plenty of Native American genes went into the pot as well.

Some African tribes had blue eyes. And the original Brits were dark-skinned with light eyes; this has been deduced from Cheddar Man's DNA - he lived here 10,000 years ago.

It's nowhere as straightforward as AA+BB=AB. Have some nice pictures 🙂

I have green eyes
DH has brown eyes

DC 1 brown eyes
DC 2 blue eyes
DC 3 green eyes
DC 4 blue eyes

It isn't as simple about blue being recessive and brown being dominant as it was taught in high school science. A person can have the gene for brown eyes but lack pigment so they may look blue eyed but they carry the brown gene. So two blue eyed people can absolutely have a brown eyed child.

Our son has brown eyes, daughter-in-law has blue eyes. 3 of their 4 have blue eyes. They both have dark brown hair, one son is very blond with bright blue eyes, and the youngest has brown eyes, but light golden brown hair.

When our kids were young, we used to say we have the variety pack. We have six kids, no two have the same hair and eye combination. My husband has brown eyes, I have blue eyes. On top of that, my husband and I have brown hair, but 3 of our kids are redheads. So we have:

-brown eyes, very dark brown (almost black) hair
-brown eyes, red hair
-blue/green/gray (depending on light and what she's wearing) eyes, dark brown hair
-green eyes, red hair
-blue eyes, dark brown hair (was very blond the first few years)
-hazel eyes, red hair

It's often assumed we are a blended family, or some of our kids are adopted. Genetics are fascinating!

Because, funnily enough eye colour is somewhat more complex than the brown = dominant, blue = recessive that is taught in GCSE biology....

A friend was surprised when she had a brown eyed child - as both her and DH had what she had always thought as blue eyes. Both parents had greenish brown "specks/patches not sure how to describe it". All four grandparents had brown/hazel eyes and child's two siblings had blue eyes.
Sure makes life interesting that nature brings up so many differences. And stuff we learn in primary school science gets proven to be not quite as straightforward once we move on to higher level biology.

I'm green eyed. My ex is brown eyed, our son has bright blue eyes.

My elder son has blue eyes, my daughter in law brown. One grandchild has blue eyes, the other brown. 50.50 chance

Not really. If it's been blue for a number of times then the chance of the next being blue increases, there are more factors involved as others have said. If you have twins then the probability of another set of twins increases. It's not the same as coin tossing where, excluding an unfair coin, there are no other factors involved.

Blue eyes are recessive so if they have one blue and one brown gene they will have brown eyes. If both parents have one blue one brown then It's a 50/50 chance that they will get the blue or brown from one parent. I guess the chances are lower that they consistently get the blue gene from both needs to have blue eyes no idea how to work that out but obviously has happened in this case

Think about a jar of marbles. Your DH and you each have a jar with about 8 marbles in it. If a single one of those marbles is brown and the others blue then your eyes are brown.

Your eyes are also brown if there are more brown marbles.

Your child's eye colour will depend on the 'marbles' you both pass on. So if you get a third jar and take half of the marbles from your jar and half from your DH's if there is a brown marble then their eyes will be brown. But it might be that you and your DH only have 1 brown marble each so you both pass on only blue marbles.

I don't understand biology but I do understand statistics.

If brown or blue eyes are equally likely, then the odds of all 4 DC is 1 in 16 or about 6% so unlikely but not impossible.

But across a population, if you have 16 families of this heritage mix all with 4 DC, statistically one of those will have DC all with blue eyes.

The same will apply even if the odds are lower. If brown eyes are 75% chance and blue eyes 25% chance, then its 1/4 x 1/4 x 1/4 x 1/4 = 0.4% or 1 in 256. So if you have 256 families, then one will have all blue eyes. A million families then
4000 will have this combination.

That's the point that a lot of people seem to overlook. No individual will personally know sufficient people for the people they know to be representative of the population as a whole. But they could quite well know one or two of the minority who fit whatever criteria is being considered.

Works the same for boy/girl combinations, finances, illnesses etc. Even if your personal observation suggests that 'everyone' or 'no-one' does or doesn't fit a certain criteria, unless the sample set you're observing is representative of the entire population, which is extremely unlikely, then no definitive conclusion can be drawn.

As previous posters have said , it’s less than a 1 in 2 chance of being blue eyed from brown eyed parents. Both my parents had dark brown hair and brown eyes but I’m a a blue eyed blonde ( well mostly grey now!)

No-one can tell you as it depends on the genotype of each parent. If you tell us the eye colour of each parent it would be possible.