Should petrol money and accommodation be charged?

Of course person C should pay a third.

OP, why are you only answering to one of the very few people who said C shouldn’t pay?

I'd expect C to pay somehow, perhaps as suggested doing the food shop.

If I was A, I would be conscious that C is my family member and I have invited them by my own choice to make them (and likely myself) feel better. I don't think A has thought about the impact to B.

Whilst B has agreed, it was not the original plan and the holiday they have paid for has now changed, possibly to their detriment. I wonder how much choice B had in agreeing or if they were guilted into it. Does B still want to go in these circumstances or can they 'give up' their place to C and be refunded by A/C?

C has agreed to go along - but what did A say to them- was it 'just come along' or was it 'you'll need to chip in'. If C is a child of A then this will affect their expectations of A. C is unlikely to care about how B feels either.

So between A & C who are seeing the benefit they should be compensating B for the change in holiday - so reducing their costs in some way, not necessarily a 1/3.

If I were B, unless I was a very nice person (which I'm not) I would be quite annoyed.

Months later, person C, who is a close family member of person A, is going through a tough time and was invited to tag along on the holiday as they live alone and are struggling.
Yes, A asked B and B is fine with C attending.

I bet that they were invited by A, who then asked B if it was ok after the fact, who probably felt they couldn't say No at that point. They may be going through a tough time but they should still pay their way.

No idea how to vote because I have no idea whether being unreasonable means I think that C should pay or that C shouldn't pay.

However, I generally think that C should pay. There will be less space in the caravan with three people - yes, there is room, but clearly A and B rented the bigger caravan knowing it was only two of them because they wanted space. Less room the car (though probably not that big a deal). More need to deal with an extra person taking a shower/using the bathroom, etc.

Though it depends, as other have said, in how the invitation was given and in the individual circumstances. But, given that it appears to be an argument, looks like A and B (or at least one of them) who knows the circumstances still thinks C should pay, so I'm sticking with C should pay.

Yes c should pay a third of accommodation and petrol, it would be an odd dynamic for only 2 to pay and c get a complete freebie.

If A is happy to subsidise their close family member that's up to them.

As everyone else has said Person c should pay.

I'd be looking to see if person c could pay whoolly for petrol rather than giving A&B money back but always depends how much stuff is.

Accommodation £150 each - total £200 paid by A&B; Petrol £100 - unpaid - Trip total £300 = 3x£100

then person C can pay £100 which can be used for petrol alternatively put any additional money into a kitty for use on the trip? saves giving money back to A&B?

C can't expect a free holiday.

A can trump up the funds if they feel so bad about leaving C alone.

As it's a caravan, it does change things, not as if it a 3 bed cottage with a whole bedroom going spare.

Myself and my good friend Anna were going away on holiday for a week abroad many years ago. My best friend Beth, also mutual friend to Anna, said she'd love to have come if she could have afforded it.
Anna and myself had a discussion and then both suggested that if Beth could afford her flight, insurance and spending money, she was welcome to join us. Which she did. Anna and I stood the cost of the villa and hire car, as it was already paid and we were happy doing that, as we were going anyway. Beth did her fair share of housekeeping to pay her way, without it being expected. It worked well all round.

C should pay for their share or A should cover it. b has gone from having a trip with a mate in a big enough caravan for lots of space presumably it’s this big because you both agreed you wanted the space.

Adding a third person uses this space with was agreed upon as wanted extra space.

Most three bedroom caravans are also two twins and one double. If en-suite the double gets that’s too. If not you’ve now got three women clambering for one bathroom rather than two just sharing it. Or is it only a 2 bed and now someone’s going to be kipping on the sofa dictating bedtime basically? Tip toeing in the morning around a sleeping person to make a drink.

Surely it depends on the basis that C was invited, and the particular circumstances?

If C was down on their luck and A & B invited them by saying "we're off on holidays and we've got a room going spare and an extra seat in the car, would you like to use them?" then I'd say that C was being offered a free holiday and they probably accepted on that basis.

If A & B asked C to come along saying - "would you like to come on a joint holiday, the accommodation will cost £x, travel will cost £y", then C is agreeing to pay their share if they accept.

If C is not paying for the holiday, I'd hope that if it was affordable that they'd offer to buy the booze/pay for a takeaway/do a grocery shop in appreciation of the free holiday.

If I was A or B, I would just suggest C pays for the petrol as the accommodation costs are already sorted. That way it's still cheaper than they were expecting and C is contributing.

It should also be fairly easy to say to C 'we've sorted the caravan so no need to worry about that, you just pay for the petrol'.

B should pay a third.
A could pay for C’s third as well as their own if they want.

The holiday isn’t costing any more so I’d be fine with C not paying. I would expect them to do more than their share of food shops and pay for a meal out.

For me, a lot would depend on the circumstances of person C. They have been invited to cheer them up as going through a tough time. If they are struggling financially I wouldn't ask, as ultimately it won't cost A and B any more than if they weren't coming. I'd maybe suggest they pay for you all to go out for lunch or dinner one day.
If they aren't struggling financially then I would just split it. There is no reason not to really, just if I knew they couldn't really afford it I wouldn't want to make them. That said, I have friends that would rather push themselves into hardship than accept any kind of freebe as opposed to all the CFs on MN! (as in posts about CFs - not calling MNers CFs!)

Id expect c to pay, if a doesn't because they are family, then it should still be worked out what c's share is, and b get offered half of that if a is happy to pay for their relative

It's up to person A and person B. If A doesn't want money but B does then maybe C could pay 16% of cost to C.

The other option is that C could pay for all the petrol.

There isn't really a clear right or wrong here

From post you are inviting C because they are going through tough time and you are being nice. It wasn't to reduce overall costs to A and B. Therefore if C offers to contribute then accept a token gesture but not full 1/3 whack.. obviously they pay for own food and extras but not accommodation or fuel.

Either person C should pay a third, OR person A should cover their costs as they invited them. The cost for person B should definitely be reduced because they are not getting the same holiday they originally agreed to pay for.

Off topic but I always feel like these "person A" "person B" posts are a quiz that you would get in school and they make my brain hurt so I can't read them 😂

Why wouldn't c pay?

C should happily pay. And be grateful that a and b have agreed to alter their plans and share their trip.

So C is As relative. Who is on a downer.
Of course C should pay. This had massively changed the trip for B and even if there was extra beds the extra space always comes in handy in a caravan because they're tiny space. It will feel cramped with 3 independant adults.

I'd feel a bit put out as B and even more so if I was paying the same

I think C should put the cash in a pot to be used for food and drink instead but the should contribute in someway.

How much money did A and B pay for the accommodation?

How much will the fuel be?

I think person C should be paying 1/3 but this could be done by them paying the total petrol cost. Is person C refusing to pay?

Of course C should pay a third, unless C is a close family member of both A and B and A and B agree to fund C as a gift because she's having a tough time.

I don't think I'd be amused in B's shoes if I paid half for a holiday and then A invited a family member along and thought the family member could just tag along for free.