I find it quite sad that for a lot of people lead such self-reliant lives, it sounds very isolating to me.
It has nothing to do with that at all. I would put myself out for my friends & family in this situation, only of they had the courtesy to ASK me & not assume that my trip/life/time was less important than theirs.
6 days is a MASSIVE ask. 6 days with a naughty kid, is way beyond massive. Added to that no one respected me enough to ask me, no sorry, you're on your own!!
But- DID you actually ask her or did you assume? That makes a big difference. If you read (even just the op's) other posts, you will see that the op & her mother ASSUMED that the sister would do it. No one even mentioned it to the sister UNTIL it was clear that the sister intended to carry on with her weekend away, at which point the op called her to give her hell for not dropping everything & bailing her out. No one had the courtesy or respect to ask AT ALL! That is why op is BU.
PS your sister is obviously jealous of you, because you're in a stable relationship and she's not. C'est la vie. So single parents are jealous of the married siblings? I doubt it.
This is nothing to do with being jealous. It is to with it being assumed that you would cancel your long awaited (childfree) weekend away to look after your nightmare nephew for almost a week, because his parents can't be bothered to do it themselves.
Let's face, that is what it comes down to. It isn't a child free wedding, it isn't impossible to take the child, they can obviously afford to take him, the parents just don't know how to manage his behaviour, so won't take him into situations that they feel will test them & lead to disapproving looks (which again is nothing to do with how her son would feel to get those looks, he won't care less, op doesn't want to be judged on her parenting)
They are copping out & expecting and assuming that someone will pick up the slack. OP has blamed her mum, her sister, her mum's boss, the guy who left his (high pressure) job.
When the blame is at her & her dh feet for not learning how/wanting to manage their son on a flight. They want an easy life for a week, so are assuming people will be running to do it for them, even if they don't get asked nicely.
If I needed help I would ask. If someone was willing to help, I would also adjust my flights & fly in as late as possible, and out as early as possible, making the time my friend/fmaily had dc as short as possible. I wouldn't just take it for granted that childcare would magically appear!!
Yes, it was the mother who first asked the sister if she could change her plans. SHE DID NOT!! No one asked the sister. They both assumed the sister was going to cancel her weekend to have the op's child until sister announced she had found alt childcare! Which was a couple of days down the line. IN WHICH TIME, NO ONE HAD ASKED THE SISTER TO LOOK AFTER THE NEPHEW.
This does mean no restaurant meals out as a family at the moment, and I do balk at taking him on a long flight. To be honest op, how will he learn if you don't put him in those situations.
Why are people saying well done for apologising to the sister? When you are wrong, you apologise. It isn't something to be celebrated or praised for.