To bring DD friend away instead of DSD

Well, seeing as your dd didn't get invited on any of those trips it makes the pair of them CFs of the highest order!

"Hello Ex...I think there is some sort of confusion over my dds birthday trip. I am the one solely paying for it and aside from me no other family members are going. It's not a family holiday but a mother/daughter trip for DD and the best friend her own age that she has chosen to keep her company. Could you perhaps gently explain to DSD that her not being included in DDs birthday gift isn't a personal thing - her father and DS are also not coming? It's very similar set up wise to the holidays you and DSD go on and obviously I'd never dream of suggesting you take my DD and DS on your personal holidays together. Perhaps if she could reflect on your past holidays and the upcoming holiday to Greece she would see that there is no unfairness or ill intent - DSD has had holidays with you and my dd is just having a mother daughter trip with me on this occassion."

What happens when it’s his daughter’s birthday? If you’re treating the children vastly differently then that is very unfair. What you do with your son is irrelevant to this particular issue as is how her mum treats her. Taking a friend abroad for an 11th birthday is a quite unusually large treat for one child of the family. It’s fine to say that you’ll do equivalent for each at some point before they’re 16 and let them choose large party etc but it’s not fine to favour one

The dad isn’t arranging this trip. If he arranged one for his older daughter, he’d have to do something for his other children as well, to be fair.

This is a mother / daughter trip. If DSD wants the same, her mother should arrange it.

Dad has nothing to do with it.

This should have been in the OP. It does change things.

It boils down to this.

The step-daughter's mother may not be able to afford a trip like that. This makes it unfair in my eyes.

This is the adults' problem to solve.

Why not the dad?

I do agree that her dad could offer her a similar birthday treat though. As it could seem like they are being treated unequally otherwise. It’s not fair as you are paying but kids don’t see it that way.

The mother can do this

I can’t believe the mum texting you that 😂

If it was a family holiday and you were leaving DSD out then fair enough. But you going away with one of your children and her friend as a birthday treat is totally different.

Very strange behaviour!

I don’t have stepchildren but 2 children of my own. I’ve always said I will try and go away with them individually for some bonding time, I think a city break is a lovely idea.

If her mum is willing to pay for this and organise it, then I don't see why not?

That’s up to her own mother, isn’t it?

treating people equally does not mean treating people the same. It’s DDs birthday treat and her preference is to take her friend. Totally reasonable.

DSD should also get a birthday treat of her choice. If she for example, decides she wants to go to a London show, will she have to take her sister? I would think not - she’d probably rather take a friend. This is equal treatment.

the same would apply to full biological siblings - at ages 11 and 15, they are likely to prefer spending times with friends than each other.

Can dsd get a similar trip instead for her and a friend ?

Of course she is being bratty. It sounds like she has had plenty of holidays with her mum, and she has another one planned. I'm guessing that she isn't arguing that her younger step siblings are being mistreated if they aren't being taken on these trips as well.

This isn't a family trip from which she is being excluded. It's a mum/daughter trip for the 11yo's birthday. The older girl has done her own trips with her mum, which I'm pretty sure the 11yo wasn't invited on. At 15, she is old enough to understand this.

It's your daughters birthday ... what does DSD has to do with this trip is beyond me so no yanbu. Enjoy your trip and explain kindly to the involved parties that this is her day and her decision as to who she wants there. I think it makes it better that her brother is not coming as well as it obviously means it's nothing personal.

And did you demand that your children went on those trips as well, in order to ensure fairness between siblings?

I'm guessing not. Quite why anyone thinks it should be different when you're taking your own dd away, I'm not quite sure.

God, the nasty language towards a fifteen year old here from some posters.

'Bratty'

'Moody, aggrieved little prick'

She's not. She's 15 and understandably jealous that your DD is getting a trip away and she isn't. Doesn't make her a bad person.

OP - you're not doing anything wrong, but it's up to your DH to think this through and see whether an equivalent can be offered to his older daughter.

Edit: just seen your update. All someone needs to do is point out to 15yo DSD that she has had plenty of trips too.

This isn't step and bio children treated differently. Read the OP - the youngest (bio sibling of the DD) will also stay home. It's about one child getting a birthday treat. As long as the other 2 get age-appropriate treats of their own on their birthdays, no issue.

This makes no sense. Surely the comparable situation would be for the dsd's mum to take her to New York, and the comparable question would therefore be whether the OP should demand that her dd should have the right to go with them on dsd's birthday trip.

YANBU

Given that neither of the DSD parents or the DSDs siblings are going away, then it's batshit of the mother to question the OP.

Assuming that if your DH took dsd away for a trip to New York, dd and you would be fine about that? If so, crack on.
Is DS your dh's child only or yours too?

This is not a reasonable comparison. Dad has nothing to do with this trip.

The fair comparison is if DSD mum takes her to new york for her birthday, which OP presumably would not mind in the least.

The nicest thing would be for her Dad to take her and a friend on a comparable trip for her 16th.

Well no, Dad isn't takimg younger DC on this trip, her mum is. It's DSDs mum who could take her away.