Cf parents or me?

Jeez that's really really shitty of your parents!

Sell the fucking ticket for as much as you can. Tell your parents to go to hell.

You are certainly NOT selfish

What is your relationship with your sister like?

It's YOUR birthday, not your bloody sisters. I bet you've spent years accommodating her needs. You really need to stand up for yourself and tell your parents, you can't and don't want to go. They should have actually asked you before shelling out £300 on a ticket, so it's their problem.
It'll probably cost you money to go too, travel, eating, child care etc.
Time to stand up for yourself.

I'd tell yoir parents you need to buy dc a bed so you are selling your ticket

This - and the other posters who said the same.

Oooof. That’s tough.

I have two sons. One is autistic. Their birthdays are days apart. I work soooooooo hard to ensure that their celebrations are completely separate and that they get what they want, not what their sibling would like them to want.

I have no idea how you’d raise that with a parent though. Maybe brutal honesty. “Mum, I appreciate that you thought I’d like this ticket, but it’s actually just made me really stressed. I’m going to sell it to buy a new cot and to get some cheaper treats I’ll really cherish.” (Then hope she buys it off you and makes it much easier!!)

No, I think that is lousy OP. That's like getting a babysitting job for your birthday. Sell it!

I can't understand their thinking at all.

Surely, if your sister needs someone to accompany her, then they spend £600 on getting your sister 2 tickets and support her to find someone to accompany her.

However what sort of Parents / Grandparents would spend £600 on letting one dd go to a concert of an act the dd has seen 4 times without these tickets, but let the other dd live in temporary accommodation and be worrying about where food and nappies are going to come from

I agree with everyone else - that's a mean present for you. Do they know your financial situation? I'd tell them you're planning on selling it, & they can have first refusal to buy it. If they don't want it, sell it and buy your baby a cot.

They should buy you your own birthday present!
How thoughtless!

If they want you to accompany your sister they should buy you a ticket separately to your birthday gift and ask if you are happy to go with her as a favour first.

I would tell them outright exactly what you have said here.

YANBU.
Tell your parents one of them should go with her.
Even if you don't get an alternative gift, it's worth making the point that "the gift of chaperoning my sister to a concert I have no interest in" is no gift at all.
God, how can people be so obtuse!
Don't go, it will ruin your birthday. Go have fun doing something you like instead (and try not to think about the wasted £300).

Taylor Swift? That is a lead booker event so resale may be tricky.

No it isn't. Sell it OP!

Bloody hell, I got annoyed when my mom gave me a pair of shoes for Christmas that were originally meant for my sister.

Taylor Swift? That is a lead booker event so resale may be tricky.

If not Taylor, get that thing on Twickets!

Really unfair OP. Tell them you'll be selling it and offer them first refusal. X

they're probably being thoughtless rather than unkind.
(when i buy my daughter - not autistic - tickets as gift, i usually get 2 and she chooses a companion. usually her sister but not always)

In your shoes i would point out to your parents what you said here and ask them to sell the tickets back to where they bought them (for fan resale) or one of them to use them

You may have to be explicit in what sort of gifts you would like in future. They probably think they're giving you a nice change from a stressful life?

No you absolutely shouldn’t let it go. This is awful of them to prioritise your sister. Do your parents understand you are a separate person or that you really need cash?

I agree with PP: Offer it to sell it to DP for face value

If sister needs a chaperone, both tickets should have been her present.
Then £600 for you for your birthday.

Agree with others - tell your parents the ticket is being sold, and would they like first refusal.

That is ridiculous. You need to tell them straight how you feel about that.

I think that's really thoughtless and unkind.

I would let your parents know you will sell the ticket as you aren't interested in attending and could use the money. They can buy it, if they want.

Do not let this go! Return it to them and tell them that you could use things for your children not their child.

No, that is not a birthday gift for you. I agree you should sell it if you can. The most I'd do would be to offer to go with your sister as a favour to her and your parents, but it shouldn't come at the expense of a gift that's actually for your personal use and enjoyment.

Tell your sister/ parents first (to give them first refusal) but definitely sell it!

Sell it and divorce your family

That is awful of them, try to sell the ticket.