I don't want to contribute to Sister's health treatments. t

Sorry about your sister.
No, you're not being unreasonable. The family have chosen to spend their money on making her last months more enjoyable and supporting the DC's education, which is absolutely up to them, but doesn't mean others need to step in when it comes to medical care.
It she has a terminal diagnosis, treatment is unlikely to do more than prolong the last stage. If a miracle cure is suddenly available since they spent their money, that's different, but unlikely.

@SILDilema

My judgement is clouded because before all this she was quite horrible to me and that hasn't changed recently either.

If this is the case & they're only talking to you because they want financial aid then I can understand your feelings about that.

There is an air of jealousy in your post that you feel they spend frivolously however the lifestyle they have is theirs & they can continue to do so even if your lifestyle isn't the same.

They're obviously keeping their life as is to give the children stability but it doesn't mean they should expect less wealthy relatives to help subsidise this.
Hopefully they have made financial plans for after her death so their children's lives can continue the same

Offer practical help to her & her family - usually worth a lot more than financial help.

I mean if it would mean saving her life or giving her an extra decade with her kids I would definitely incur some financial hardship to get her there. If not, I probably wouldn’t.

I wouldn’t be selling my house or anything like that, but maybe take out an affordable loan.

It doesn’t sound like that’s the expectation though.

What have they said to drop the hints?

If this were my sister, I would be loosing my mind, especially considering she has school aged children! Definitely not thinking about money! No one has asked you explicitly for money though?

private health care for terminal cancer is usually a scam

No, YANBU. This is sad but you contributing financially does not in any way reflect how you feel about her, and you should not feel obliged.

Had similar with my cousin. He is very wealthy - owns land, several big range rovers, own business, two houses - yet he did a gofundme to go to America for new treatment for a lifelong condition. I owned nothing - not even a car, didn't have a mortgage on a house - and there were mutterings about how I should have donated. But, he could afford to sell one of his assets and pay for the treatment and he'd still be wildly better off than I was.

Just because it's a health thing, doesn't mean other people should be obligated to fund it. Particularly when the person in question could actually afford it if they just adjusted their spending a bit.

@SILDilema Having been through the death of my daughter, leaving 2 children, not even teen, I would say not to donate. you wont help her live, you might just extend for a few months. it sounds like she has had quite a while so she has managed a good few things on her bucket list. what country are you in? who has hinted for financial assistance for her? it sounds like her partner might be a high earner. health care in UK is free. even private is not necessarily better. is this assistance needed to try a new drug with no guarantee it will work??

I wouldn’t be paying their private school fees Ld funding lavish extras that you don’t even do yourself, no.

Yes, agree with this. Of course they haven't disrupted their children's lives even further.

You don't need to give financial help, but nothing you've described is unreasonable on their part either.

Maybe you are hearing hints that they are not dropping.

I think that if they want contributions, then they must actually ask directly to avoid misunderstanding.

It seems like they have resources. I don’t think they are asking.

You can volunteer time, helping out.

Your username is SILDilema - is she your sister or sister in law?

I don’t think you need to contribute financially, but I would simply frame it under ‘we can’t contribute financially’.

No, you don't have to.
YANBU.

OP sometimes a hard NO upfront saves months of nagging.

Delivery is everything, "I can see it will be expensive, if we had money to help we'd offer it, but we don't".

On repeat as needed I'd expect you'd need to say once or potentially a few repeats.

You don’t have to financially contribute, you shouldn’t be guilted into it. Reads like you’ve always had a difficult relationship with your sister, many people will say ‘but she’s your family and she’s dying’ but sadly that doesn’t undo years of hurt. Give as much as you’re emotionally capable but not at a cost to yourself. As someone who was in a similar situation, the outside world may judge but the long term consequences to yourself won’t be seen.

That's EXACTLY how it reads!

What do you mean by saying she was/is horrible to you?

I agree, the tone is a bit….off.
Of course OP shouldn’t give money if she cannot afford it and in fact, even if she could, she’s under zero obligation. However, it sounds like they tried to carry on with their lives despite a terminal diagnosis and I cannot blame them for that!

I don't think you should have to contribute ? Not to be a horrible person but what do you do when she is gone keep propping her family up ? She and her husband (I presume) need to make a plan financially and think of the future

Perhaps the various bucket list exotic holidays were because they knew they would be her last chance to do them?

She may have life insurance, the school may help.

Just do what you can for now.

I’d just make it very clear that as much as you feel for them all, you’re not in a position to contribute at all.

Exactly!!

They’re keeping the kids in private school, because that is the best thing for them.

Their entire lives have been turned upside down and the mum just wants them to have as much stability as they can in such an awful situation.

Like the pp I’d offer practical support such as transport , cooking etc but nothing financial .