How would you split the cost of this trip?

I think 60:40 between child with family and child without (if non birthday parent is retired) or 30:30:40 between single child/ parent and child with family (if non birthday parent is working). Revise as appropriate if someone is incredibly well off (eg really rich retired parent should be nice and pay for the whole family) or really struggling (eg the family with the teen even if both adults working might be hard up if on NMW). As a general rule you should be arguing about who puts in MOST not least with family. If that's not the case probably don't holiday together as it will only get worse.

We’re going on a family holiday next year, and we’re all just paying for ourselves, partners and respective children.

Split the cost by number of people going, everybody pays their amount of people.

I wouldn’t dream of paying for my brother because he’s single and earns less. I wouldn’t pay for my sister’s kids either - I’ve got my own to pay for.

When we did similar for my stepdads 60th we did it the same way, but split the cost of him between the paying adults. We didn’t pay for my mum, and she didn’t shell out for all of us either - it was only his birthday.

I think you split per person then everyone chips in for the Birthday adult.
That way the person with a child is paying for that child as it doesn’t seem fair on the single person to pay a portion towards the child.
So are you just asking for advice prior to making a decision with your family or are you having a dispute over this with your family?

In my mind (making up a scenario much as others have done) this sounds like a joint thing - where you've all gone 'what shall we do for Dad's 70th? How about we all go down to Cornwall together? Ooh great idea, we could book a big house!'. Rather than one person forcing the idea on everyone else.
Or tbh, even if its not that, assuming everyone is happy with the idea of contributing something to the cost, then it doesn't really matter who's idea it is, its just a case of making it 'fair'.
I do the whole big house thing with a group of friends quite often and we generally split it between adults. In your case I'd just remove the birthday person from the equation and split between the 4 remaining adults.

My parents would do that.

One parent organising with the adult dcs a few days away as a surprise. Very similar to what the OP describes.
The parent would be paying.
None of the children would say it’s their birthday gift though and would plan separate gifts to give to the parent. (And a meal etc….)

@GetBendyWithWendy thats how we do it in my family i should say

@GetBendyWithWendy

this is how we do it, and in personally wouldnt organise a birthday week end any other way.

• if my parents organise it. For instance my dads 70th, or if one of my parents organise it for the other and wants to make it a family (just us children with our partners and our own kids), my parents i know would pay for the accomodation.
• if we organise it for one parent. For instance my dads 60th birthday (we baught ticket for the The Ring tetralogy by Wagner at the opera in Vienna - my parents are big into operas), we paid for 2 tickets for the whole lot, 1 meal out with wine and champagne, and they sorted out their accomodation and flights.
• for my mum 70th we took her to rome, she sorted her flights, we paid for the 1st meal and hotel and visits, she insisted on treating us for another meal.

in your scenario it is either your parents pay the accomodation or you siblings share the accomodation between you and treat your parents. Or do something cheaper.

That’s true, but equally if 2 parties have more available cash than the third, they might make assumptions based on what they want and can afford. Then the third party looks mean or churlish not to join in. Families can exert a lot of guilt or other pressure.

If it’s the other parent’s idea, again- if the split disproportionately impacts one child, it seems unfair to insist on equal splits. My parents used to invite my sibling and me to holidays because we didn’t earn very much and couldn’t afford to stay in the sorts of places that they wanted to stay in. They’d rent a place and we’d make our way there and probably invite them for a meal or do all the chores between us, that sort of thing.

I feel that it depends on how you see things.

Is it a holiday that you organise and you decide to pay ‘for mum’. A bit like the example in a PP - you organise a surprise birthday meal and say ‘mum that’s for your birthday. We’re paying’.
Then you’d expect people to pay depending on the number of adults. It’s just a holiday and your gift is basically paying for the parent’s share of the cost.

Or is it a gift to her that involves the people she cares most about? Is it Something organised around the parent only? So the gift is the holiday, centered only around the parent.. In which case, it’s divided in 3 for the 3 gift givers.

Depends on who is organising the surprise:
If parent is organising for other parent, parent pays.
If adult children are organising then they pay for both parents

Are you the spouse of the birthday guest?

Happy Birthday!!

They can take it up with their spouse if they have a problem!

Each adult pays their own share and the parent of the teen pays for them. All the adults pitch in to pay the cost of the birthday surprise.

So the parents birthday present is a massive bill for a holiday they didn't even choose?

I think with hotel rooms everyone just pays for their own room, with air BnB type homes I think just split the cost by the number of people going as you all have use over shared facilities. If, for example, three bed works out to £100pp but because there’s a child and a 4 bed is needed it ends up being £200pp I would expect the couple to fork out more. If the child is sharing a room or the cost is negligible just share it equally amongst each adult.

The parents should pay for everyone.

This seems the reasonable 2 options.

OP - what cost split is actually being proposed?

not every married couple has shared finances.

But I think the point they are making is, if it is the children's idea and they are doing this as a gift for parent A, asking parent B to contribute is cheeky.

If it was parent B's idea then they should be either paying for it all or paying for themselves at least.

Who's idea was it??

Whoa - it's a fair point on the face of it, but that way lies "I've had a lot of expenses recently" and "Ah, but look at that expensive such-and-such you bought"

To my mind it's up to each family unit to decide for themselves if they can afford to go, and if they can then tthey should expect a fair split

I would be super surprised and pretty annoyed as we make financial decisions together and don't have a lot spare. But that's irrelevant.

I still think it's based on the number of rooms as if the teenager has his own room then he counts as a person. If he's sharing with his parents then he's a child.

who's idea was it to do this as a surprise? Was it you and your sibling as a gift, or the other parent? And how many bedrooms? Those are all crucial to work out 'fairness'.

If it was you and your siblings idea you should each pay a split based on bedrooms, and share the cost of the parents bedroom.
So if 4 bedrooms
you pay 1.5
sibling pay for 2.5

If it was your parents idea then it should be
you pay 1
sibling pays for 2
other parent pays for 1

everything else should be split per person with you and sibling potentially covering your parents.

Split equally between all adults.

Also depends on both incomes, and whose choice the trip is. If one party earns significantly more than another then that might need to be recognised when splitting the cost.

I would probably expect the parent and two children to each pay a 3rd for the birthday parent and then each pay for themselves plus partner/child. The person whose birthday it is should not have to fork out for their own surprise, the single childless person should not have to pitch in for the cost of partner and child of their sibling. If each 'unit' pays their own way and a share for the birthday person, all is fair. Alternatively you may want to take into account the state of each person's finances and split the birthday person share unequally if for example one of your children earns significantly more than the other or the coupled-up child has more demands on his money i.e. partner and child, he may require a discount on his share of the birthday parents trip.