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AIBU?

Share your dilemmas and get honest opinions from other Mumsnetters.

Original poster

When they're not actually brothers!

263 replies

3isthemagicnumbersoimtold · 28/06/2017 22:40

I have three children

DS is 10 and twin DS are 7. My BIL and SIL have a son who is 9. From when he was born they've always been very set that he would be their only child. Fair enough not my business.

Anyway my boys are very close and get on well with each other. twins are identical and very close and older DS is a good big brother to them.

They get on well with their cousin and see him once a week (perhaps every two weeks) at my MIL. He's a lovely boy too and they get on well.

Anyway, last week they were upstairs playing and nephew came downstairs very upset saying my oldest DS had been mean to him. I asked DS to come downstairs to explain what was going on. DS came downstairs and explained that my nephew (his cousin) had said to him that he's just as close to him as the twins and they're brothers too. I think DS was maybe a bit blunt and said that cousins weren't as closely related as siblings. Nephew said that my BIL and SIL had told him they were as close. I quietly said to DS that he shouldn't hurt nephews feelings and that he wants to be as close as my DS is to his twins brothers, it wasn't harming anyone and it's lovely that he feels close to them.

Anyway, that was that I thought. But no, i had a text from my SIL who said she thinks my DS is incredibly mean and rude for telling nephew that he is not as close to them. I don't even know what to reply to her. It's just bonkers! They're not brothers!

I feel like I've been dragged into a strange argument that biology and genetics would set straight! Aibu to just tell her to piss off?

OP posts:
monkeymamma · 29/06/2017 15:48

Charleymouse that's fascinating. I have always wondered how come I am so like my cousins on my dad's side (also his twin's children), we were raised on separate continents but have weirdly similar likes and dislikes - like loving the same foods and having all the same medical ailments!

Original poster
3isthemagicnumbersoimtold · 29/06/2017 15:49

Wait does this mean that you're not as close to cousins on your mum's side?

Surely that is a load of nonsense. You're not more of your father than your mother. His sperm isn't more important than her egg...surely!

OP posts:
Lweji · 29/06/2017 15:51

You are more closely genetically related to cousins on your fathers side therefore should not marry etc due to effects of consanguinity.

Complete bollocks.

PsammeadPaintedTheLion · 29/06/2017 15:53

Sil likes to tell anyone who'll listen that my two children and her son are growing up 'like siblings'. They are close, they see each other most days, but they are not 'like siblings'. It riles me but I've never said anything because it would be insensitive.

Your sil has taken it to the next level though! They've filled the kid's head with this nonsense and set him up for hurt, instead of just being happy that he had a great relationship with his cousins.

Lweji · 29/06/2017 15:54

Actually, we share more on our mother's side, because mothers transmit mitochondrial DNA to all children.

So, in fact, we share more DNA with the children of our mother's sister.

Lweji · 29/06/2017 15:55

You're not more of your father than your mother.

We are always more of our mother than our father.

Original poster
3isthemagicnumbersoimtold · 29/06/2017 15:55

monkey

I can't make DS pretend they're brothers and I don't think it's fair of SIL and BIL to force the issue. It's like me forcing my twins to treat their older brother as their triplet I guess. It just wouldn't happen

OP posts:
SumThucker · 29/06/2017 15:56

As Lweji says. A Doctor told me that recently.

DrinkFeckArseGirls · 29/06/2017 15:57

Is your SIL foreign? Where I'm from
we call first cousins "brothers/ sisters through Aunt" - bracia cioteczni/ siostry cioteczne.

AndTakeYourHorseWithYou · 29/06/2017 16:00

You are more closely genetically related to cousins on your fathers side therefore should not marry etc due to effects of consanguinity

Um no, it's literally the exact opposite. You are genetically more related to your mothers side.

Charleymouse · 29/06/2017 16:01

monkeymamma it is fascinating isn't it.

I know biologically you are the same relationship however if you are male genetically I think you are closer. Beats me how it all works but interesting nonetheless.
Hopefully someone cleverer and more informed than I can shed light on this.

Lweji · 29/06/2017 16:02

if you are male genetically I think you are closer.

No, FGS.
We've already explained.

Charleymouse · 29/06/2017 16:03

Andtakeyourhorsewithyou that is what I always thought but why is that? Someone explained the Y chromosome thing to me recently and it seemed to make sense.

Lweji · 29/06/2017 16:04

Did you miss my post about mitochondrial DNA, or are you choosing to ignore it?

zzzzz · 29/06/2017 16:05

This reply has been deleted

Message withdrawn at poster's request.

CouldntMakeThisShitUp · 29/06/2017 16:06

I don't think it's fair of SIL and BIL to force the issue. It's like me forcing my twins to treat their older brother as their triplet I guess

She's probably portraying your dc as surrogate siblings to her ds and that's where he got the idea from.
Her ds has probably been talking about not having any siblings and this is her way of wriggling out of telling him the truth - that he will be an only child.

Lweji · 29/06/2017 16:07

In some societies, inheritance goes through the mother's side because, let's face it, you know your mother's (and grandmother's) children are related to you, but your father's may or may not be. :)

Original poster
3isthemagicnumbersoimtold · 29/06/2017 16:14

Any quick search of the internet shows that we are more closely related to our mothers due to transmission of mitochondria.

OP posts:
HappyFlappy · 29/06/2017 16:14

'Dear Bonkers SIL. They are cousins, not brothers. Good day to you'

Missed the most important bit, Nancy.

"And now - Bugger off!" Grin

Emotionally, perhaps they can feel as close as brothers - physically it's impossible because they are of different genetic make-up.

You could point out that your son's feelings were hurt by the implication that he is not closer to his brother than the cousin is.

antimatter · 29/06/2017 16:14

I think OP you were very thoughtful and sensitive towards your DN.

Why doesn't SIL think that her words are upsetting your sons? I tell my kids that they have nobody close as each other and then they have 4 cousins.
Cousins are very close and spend time together but they aren't siblings!

If your SIL comes back with any comments tell her that actually your son was upset too. She is very selfish.

Ohyesiam · 29/06/2017 16:16

Could you find a nice easy of saying that if she taught her son about family and relations, he wouldn't get upset because he'd know the facts.

Original poster
3isthemagicnumbersoimtold · 29/06/2017 16:16

Oh goodness I don't want to go down the line of talking about DS's feelings! He isn't bothered other than being a bit Hmm and Confused at why he needs to pretend his cousin is his brother!

OP posts:
HappyFlappy · 29/06/2017 16:17

If she does not want her son upset again,

. . .she should stop feedings fantasies and explain the truth to him; that they can all care for each other as much as (she) brothers do, but that they aren't the same recipe.

Lweji · 29/06/2017 16:20

You might want to ask your SIL if she's preparing the ground for you to adopt her child.

Butteredparsnip1ps · 29/06/2017 16:21

Sil is bonkers, but not unique.

We have an extended family member who likes to pretend a relationship exists when it doesn't. It's frustrating and hurtful.

SIL is looking for validation of her choices