AIBU to refuse looking after my sister's child during her honeymoon?

It is the sisters-in-law not the PILs who are prepared to have DNiece for a week and they can't take more than a week away from the business they are running.

And I’m shocked they had the nerve to ask someone to have her for two weeks to start with.

Different for an offer but to ask is extra cheeky.

That sounds like a lovely idea

Whereas I’m shocked that the parents of the kid are happy to leave her for 2 weeks to go on holiday.

Of course you are not being unreasonable. Ffs only on MN would you get some of these responses, lol. You don’t have to justify your two weeks off, you just say no. You have done enough and have other commitments. She’s bloody cheeky to ask given everything else you have been doing.

So your sister has two children?

No. She had a baby and the baby became a toddler. The toddler is now 8.

Nope. One.

There was no resentment, just an explanation.

And OP has listed the other reasons that she wants to take her annual leave with her DH and DCs.

So your sister actually has two children?

I don’t think you’re being unreasonable at all. Your time is yours to do as you wish. You have offered a few days if that’s not enough then tough tits

It’s clearly not a ‘one off’ - they’ve left their daughter for 2 weeks previously.

Giving a holiday the title honeymoon doesn’t change what it is - a holiday.

I would suggest they leave the child for a week and you mind her for 3 days and then the ILs take her for 4, or the other way around. 2 weeks is too long for parents to leave a child i think. While I understand not wanting her for 2 full weeks, I think saying no seems a bit mean to be honest. You seem so exhausted from all the wedding planning surely you understand the bride will be more so? You also seem to resent having helped out with childcare so she could attend wedding related appointments. It's not like this is an annual holiday it's her honeymoon, I think its fair that family help out as a one off.

I'm shocked that a parent would voluntarily dump their 8 year old for two weeks in the summer holidays, without seemingly being that bothered about who with/what they'll be doing in those two weeks, when they could take them on what sounds like a pretty ideal family holiday in the south of france.
I could understand a bit more if it was a trip that an 8yr old wouldn't enjoy, if it was long haul, or something too adventurous like trekking. Or if they wanted a few days to themselves. But two weeks is a long time, and it doesn't sound like the bride has had any thoughts about thinking of a decent alternative for DN, just 'who will have her'. It isn't just about how independent DN is, it's the idea that the rest of her family gets to go on a great holiday and she's left behind.

I wouldn’t be watching anyones children for a week or two for a holiday. Bloody cheeky.

An emergency then yeah I’d have to step up and have at least a few days but a holiday nah.

Defo not being unreasonable. You sound like you do a lot for your sister in general and also with the wedding prep. And caring for your husbands family too.

It would really annoy me at your sisters in laws saying that you should look after the niece between you. The cheek of them offering your time. Let them do it all themselves if they feel so strongly. These ppl want to look good ie offering the honeymoon but its at the expense of your time. CF's

Also your sis can still go if you don't mind your niece she can take her with her. She just doesn't want too. She doesn't want to be put out but has no trouble expecting you to be.

You are not being unreasonable. The wedding is neither here nor there in my opinion. You booked 2 weeks leave, you and your husband have made plans. You are allowed to do that! You don't need to cross reference with all and sundry to make sure it's convenient. You enjoy your time off

Cant the inlaws have the kid for 1 week then take her over to France for the second week. Perhaps they can all stay for the second week.

Your in-laws are being awfully generous with YOUR free time. How nice of them /s. Please say NO and stick to it!

I’m shocked at how people treat their family too—the bride palming her child off at the nearest relative for a fortnight, and asking her sister, her BIL, and her DN to cancel their holidays to watch her daughter at short notice. An appalling way to treat your family, especially a family member who has given you free childcare so you didn’t have to pay nursery fees.

At how "people" treat their family...?

Well, I'm shocked at DSis, who has benefitted from OP looking after DNiece during bridal appointments, who is aware that her niblings (OP's DCs) have been going through exam stress, who realises that her BIL's DM is very ill and needs care, who knows that OP hasn't had a holiday since Xmas... just assumed that OP would give up her much needed AL to take her DD for two weeks.

Any thoughts on it looked at from that angle?

I am often shocked at how people treat their children. Everybody including the groom, but excluding the bride, the child's ACTUAL mother assumed that the child would go on holiday with her parents. It was the child's ACTUAL mother who wants to leave her behind.

YANBU
You have helped out a lot and it is ok to say no.

I would message her in laws and say you have said no and please respect that.

You have done a lot. You have helped her a lot. You are juggling several things. It is ok to say no to this.

im always shocked at how people treat their family. She’s your niece and I think lots of other families wouldn’t see this as the big deal that you do

But who does that? You don't just book things for people without checking they can go/have other commitments (like a child!)

Except the PILs checked with the groom, who was perfectly happy to bring DNiece (his DD) and therefore no childcare was required.