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

[Nunaluna]

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!

Lol sorry no OP 😂

I have read that if the first two are one sex, any subsequent children are statistically more likely to also be that sex. Some men have more "boy" or "girl" sperm, apparently.

My mum is one of three - GGG

I have two - BB. So if I had another, it would be either BBG, or more likely, BBB. Neither fit with your "anecdata" (although I love that word).

My 3 are BGG

BGBBB

My gran had 5, BBGBG
My other gran had GBG
My friend has BBG

http://www.ingender.com/gender-info/odds-of-having-another-boy-or-girl.aspx

This has a good breakdown of stats- it does show that families with 2 of the same are a bit more likely to have a third than one of each families. It is an American study though, don’t know whether that trend would reflect in the UK?

It also debunks the myth of being ‘way more likely’ to have the same gender again if you already have 2 boys or 2 girls.

True here, I had BGG and I am one of three GBB

however DP and siblings are BGB and I’m not aware of any miscarriages

I’m the middle of three, older brother and younger brother. All same parents. No MC.

did I provide you wrong?

So the options - with opposite sex first two -are
GBB
GBG
BGG
BGB.

50% either way. Exactly the same as any other individual child...

I have BBG but did have 2 miscarriages after number 1

Not in my sibling group.

Sorry Op my cousins are

BBG
GGB
GGB
GGB

You're assuming that each event has the same probability, which is what is being questioned.

Of those I know who have three or more in my family:

GBBGB
BBGB
GGG

i have BB and would love G

I had mine in the 70s , GBB . My brothers wife had BGG. My SIL had GBB .
My parents had BGB . My Aunt had B twin G then another B . Most other family only had 1 or 2 children . I think you could be on to something with your theory .

True for me I had BGG have since had a 4th 4 months ago who is also a girl

My mil didn’t have a tv . She had BBGBBG 😂

I actually think your on to something there

I disprove that theory. My miscarriage was my first pregnancy. Then I went on to have BGB. As did my sister. Also - my SIL had GGB .....

Sorry OP I'm one of 3 and we go GBG

Yeah I did. You said if you have 3 dc and the first two are different sexes then your 3rd will be the same as the second. You specifically focussed on what the third would be. Nothing in your OP about first and second being the same

anyway there are a pile of people giving you the answer. You are wrong 😂there is no pattern

Nope I can think of loads

I've got four - BBBG (so true for me)
My mum has three - GBB (true for her)
My aut has three - GGG (true)
Friend - BGG (yep!)
Friend - bbgb (nope!)
Friend - bgb (nope)
Friend - bggb (yep!)
Friend - bgbbggbb (true with the second half of her kids!)
Friend - BBB (true)

Thinking about it, most of my friends or people I know with 3 or more kids have followed that pattern ...but not all!

Oh hang on...I missed rhe bit about the first two being opposite sex 🤣🤣 ignore me.

There is an easy way to test this theory. Collect data from a large population of mothers with three or more children where the first two children were a different sex, count the number of times the third child was the same sex as the second and, assuming if it were random and independent the odds of having a boy or girl were very close to 0.5 (the null hypothesis), perform a statistical significance test to determine if the data differs from the expected sex distribution to a level where it can be said it would be unlikely to have occurred by random chance. If so, dismiss the null hypotheses that the sex of the third child is determined by random chance.

I believe the binomial distribution is suitable for modelling random independent trials with a fixed probability, which is what the gender of newborns is. It is not exactly 50/50, males are less resiliant than females so the coin is biased in favour of a slightly higher probability of a baby being male, kind of nature's way of compensating.

Anecdote means nothing, you need a large data sample to deduce/estimate anything useful about a population distribution.

Agree