Sisters children and step child and our holiday

Treat them all the same - as your sister would prefer. Don't take any of her children. Simple.

I think OP and grandparents want the older two there.

The younger one none of them want to mind. To be fair even teenagers are entitled to a holiday, not here’s a rota of who is minding the 7 year old while the Op has to worry if she’s safe, near water, sun cream, put her to bed on time etc

I feel really sorry for the poor 7 year old. It's like nobody wants her. What sort of dad goes away with work when he supposed to have his daughter? What sort of mother allows her child to go on holiday, with someone she has only met twice? What sort of step mother tries to palm her step daughter off onto someone else, so that she can work? And to top that off, she's not even classed as family? Just wow!
That said, it's a massive ask to ask you to take all 3 of them with you, just so they can work. It's the responsibility of parents to look after their own children, or make sure they have adequate childcare arrangements.
Personally ,I'd be telling your sister no to all 3. It's a bit cheeky to even ask.
Let your BIL and his ex sort it out.

Don’t agree when 1) there’s a very big age gap, 2) the 3 girls aren’t actually sisters.

It’s very unfair to say to two teenagers you can’t go to see your same age cousins and grandparents because the younger one would be upset.

Children don’t have go get everything they want all the time. A 7 year old can easily be told this trips is for teens. We’ll do X with you as a treat.

SD 7 has her own mums family, an entire family to hang out with that the other two don’t have.

The actual parents are the only people who should be sorting this between them. Letting your 7 year old go on holdiays with a couple you’ve met twice is insane of the mother.

I genuinely think you have been very reasonable in your whole approach here OP - and I definitely read some unkind Step parenting/ step family stuff here - this is not a case of that.

Lying reading while teens who are close organise their own days has no relation to holiday in charge of a 7 year old! Especially as you say - one who is not your own! YOu would worry about every minute of their day - I totally agree its harder than taking your own.#

I took my kids friends with us on holiday last summer and it's a huge mental burden ! worrying about whether they are okay etc - I do it for selfish reasons as my kids enjoy it - I wouldn't do it for any other reason.

Even if they were not step sisters, when there are huge gaps between siblings, they very often do different things. If not, the older children would constantly have to do activities that are far too young for them.

No, it’s actually the child’s father’s problem to sort out.

The whole point is that OP was looking forward to a relaxing holiday with her parents. Her children are self-sufficient so won't need looking after. If she takes her sister's step-daughter, her relaxing holiday is out of the window.

A seven year old does need looking after and, from my experience of being a child-minder when my own children were young and now looking after my grand-daughter who is 7, there is a much greater sense of responsibility when the child isn't your own and I couldn't/can't relax for a minute.

OP's objection isn't because her sister's step-child isn't a blood relation, it's because she is so much younger than her step-sisters and OP's children and she will need to be actively 'parented' by OP. Holidays with small children are completely different from holidays with older teens who can entertain themselves.

I don’t get this, you want to take your older nieces but not the youngest, regardless of ‘biology’ if my sister said she wanted to take my two eldest away and not the youngest I would say no too all as I know my youngest would then be upset she couldn’t go so it wouldn’t be fair.

In my view, as much as your parents and nieces want to see each other this is for your sister to sort out and her responsibility, you either take them all or none.

That would be a "hell no"! From me . Your sister is taking the piss.

Do you know for a fact that the 7yo's mother has definitely agreed to it?

Or has your sister said the mother would be fine with it but hasn't specifically told the mother all the details yet?

Have you messaged/called your sister yet OP to nip this bat shittery in the bud? X

Does the step niece have grandparents of their own to spend time with? Well done on sending the message, hopefully dsis will explain tactfully.

This is your sisters problem and she’s skilfully making it yours

The grandchildren will want to see their grandparents.
And I would NOT leave a 15 and 13 year old at home alone. Ridiculous idea.

So they get a nice child free week(s) and you get to look after 5 kids?? I’d say ‘no, not this time. Let’s all go together when we’re all free’. Then go enjoy your holiday with your husband and your kids

My apologies, I completely agree with you.

Ah, the classic “If only everyone thought and acted exactly as I think they should, life would be so much more pleasant for everyone”. Except of course people are individuals, not automatons acting out roles.

The reality is that blended families are different to nuclear ones, and you cannot expect people to consider step family indistinguishable to biological family. Some families may naturally fall into the ‘all in’ pattern of a nuclear one, but those families are far from representative. Trying to force relationships, rather than respecting and accepting them for what they are to the actual parties that make up that relationship, arguably causes far more problems than it could ever hope to solve. There was another thread recently where two kids have pulled almost completely away from their father due to his insistence of forcing his stepchildren onto them as siblings.

OP’s sister has already tried and failed to have her daughters babysit her stepchild, and now she’s trying to force the child into their family holiday. All she’s managed to do is make the child a nuisance to them, and likely cemented their opposition to ever viewing her differently.

It’s ridiculous that the only people that want her going on the holiday are two people that aren’t even going themselves.

Op is going to visit her parents who have only met the little girl twice, presumably due to living abroad, op has more of a relationship with her than that.
(I still don't think op should have to take her on holiday, just pointing this out.)

Well done OP.
Your sister has some cheek on her.

'I also find it strange that the little girls mum is fine with her coming away with us when we have only met her mum twice.'

It's always possible that the mum doesn't know about her ex's plan to send the child away with the OP. Unless it is known as a fact that she is aware, she may be under the presumption that her little girl will be with her 'D'F during his designated time, and have no idea that he is planning to send her abroad with OP's family. I wouldn't entertain doing this.

What kinds of big important jobs do all these people have btw, that they can't get even a few days off in October with 2 months notice so they could swap childcare with each other?

Another 'blended' family where the child has the nightmare of 50-50 parental care and has no place to truly call home, with parents who regard her as an inconvenience to be shunted onto the nearest available random female. I feel desperately sorry for the poor child with one, possibly 2 feckless parents, but that isn't something that the OP can solve. And no the child is not her niece; there is nothing cruel about stating this as a plain fact.

This is what I would have done, no way would I take the 7 year old.

She not biologically family and a lot younger then the rest, she will require more looking after too regardless of what your sister says.