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AIBU?

Share your dilemmas and get honest opinions from other Mumsnetters.

Original poster

Sounds mad but it’s true, honest! If you have 3 kids…

429 replies

Nunaluna · 07/05/2025 20:00

Same dad, no miscarriages to ‘break the chain’, if the first 2 are opposite sex, the third will be whatever number 2 was - so BGG, or GBB. Not BGB, or GBG.

It sounds crazy but it’s something I noticed ages ago - every time somebody announces they’re having a third, and they have one of each, I know it will be the same as the second child.

Prove me wrong, Mumsnetters!

OP posts:
godmum56 · 07/05/2025 21:05

SnoozingFox · 07/05/2025 20:14

To be fair, you have a 50/50 chance of guessing it right. And you probably forget about all the times you got it wrong.

This.

lovegoodlovegood · 07/05/2025 21:05

I can usually predict but only if I dream someone is pregnant
Had a dream a friend was and she was saying “but I don’t know boys!” She was 5 weeks pregnant, and it was a boy
I’ve just had a dream an influencer is pregnant with a girl so I’ve written it down to see if I’m right Grin

sugarspiceandeverythingnice12 · 07/05/2025 21:05

Everyone I know with 3 children (6 families) are GBG

Fourpawsblack · 07/05/2025 21:06

BGB here. Same dad.

XelaM · 07/05/2025 21:07

One of my daughter's closest friends is the middle child (girl) and has two brothers either side of her, so again - your theory is not true

AnxiousOCDMum · 07/05/2025 21:07

edited as I clearly didn’t read the message 😂😂

Etaerio · 07/05/2025 21:07

<a class="break-all" href="https://www.google.com/url?q=www.biorxiv.org/content/10.1101/031344v3.full.pdf&sa=U&ved=2ahUKEwjd_9OTk5KNAxWLSvEDHVWFJs0QFnoECAUQAg&usg=AOvVaw0l4q-Hstor4Jw99RnrjQbcThis" rel="nofollow" target="_blank">paper This paper provides an interesting discussion on evidence of correlations in sex of births within families.

SardinesOnGingerbread · 07/05/2025 21:08

Nope BGB

PinkPinkPinkBlue · 07/05/2025 21:08

GBG here

Original poster
Nunaluna · 07/05/2025 21:09

SocktopusEatsSocks · 07/05/2025 21:00

Look up how to make a probability tree OP!
For this calculation we’re going to assume a 50/50 chance of having a boy in each pregnancy.
In families with three kids :
In 50% of families, the first child will be a boy, In the other 50%, a girl.
When the second child is born, the combos look like this :
25% BB, 25% BG, 25% GB, 25% GG
When the third child is born, the probabilities look like this:
12.5% BBB, 12.5% BBG, 12.5% BGB, 12.5% BGG, 12,5% GBB, 12.5% GBG, 12,5% GGB, 12.5% GGG.
So the likelihood of a 3 child family having the combo BGG or GBB is exactly the same as the likelihood of a 3 child family having either the combo BGB or GBG.
But if you include the BBG and GGB combos then yes, you’re twice as likely to have two the same sex in age a order than either BGB or GBG. Maybe that’s why you feel like BGB or GBG is a less frequent combo?
You also have a 1/8 chance of having all boys and a 1/8 chance of having all girls or a 1/4 chance of having 3 of the same sex (either all boys or all girls).

I think you might’ve got it there! You win mystery hour this evening! ⭐️

OP posts:
GeorgianaM · 07/05/2025 21:09

I’m one of four - GBGG
My stepchildren - GBG
I only have two children - BG
Eldest sister has BBG
Brother has - BGG
Youngeat sister has - BG
Husbands brother - BBB

AthWat · 07/05/2025 21:09

Go on then, gather the data - you'll want at least thousands of cases to even start, not "my auntie and my cousin". If the data shows you are right, then you are right.

Original poster
Nunaluna · 07/05/2025 21:10

AnxiousOCDMum · 07/05/2025 21:07

edited as I clearly didn’t read the message 😂😂

Edited

That’s not what I said though. I said where the first 2 are opposite sex

OP posts:
KarmaKameelion · 07/05/2025 21:10

Huh - that is true for virtually everyone I know with three kids. The only one I know different had ivf

EilishMcCandlish · 07/05/2025 21:11

I am the G in a BGB, so no.

KarmaKameelion · 07/05/2025 21:12

Oh wait! George Charlotte Louis 😂

Original poster
Nunaluna · 07/05/2025 21:12

Tavimama · 07/05/2025 20:39

Nope. I was the oldest, then my sister, then our brother, so: GGB

The first 2 have to be opposite sex

Gah I should’ve known better than to post a thread and expect people to read the OP!

OP posts:
ClassicalQueen · 07/05/2025 21:12

I know a few people who have either BBG or GGB.

PiggyPlumPie · 07/05/2025 21:12

Nope, GBG here!

HollyBerryz · 07/05/2025 21:13

I have g b g

ClassicalQueen · 07/05/2025 21:13

Sorry I just reread this. I do also know BGB families though!

CoffeeChocolateWine · 07/05/2025 21:13

True for me...BGG!

My parents also had GBB (and then G)

Of my good friends who have 3 (and first 2 were one of each) it's BGG, BGG, GBB, GBB (then G), BGG and BGB (although not sure about miscarriages) so your theory pretty much stands up!

Eenameenadeeka · 07/05/2025 21:14

We had BGB

MsCactus · 07/05/2025 21:14

Nope - my mum had BGB

wingingit1987 · 07/05/2025 21:15

I have 5, soon to be 6.
mine are BBGGGB