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AIBU?

Share your dilemmas and get honest opinions from other Mumsnetters.

Original poster

Sisters 21st or partners 40th?

243 replies

EzWin2 · 05/06/2026 09:23

so my sister and DP have birthdays two days apart and both their 21st and 40th birthdays fall on the same weekend. I have been with DP for 11 years and we have children together. He made it clear he doesn’t want a party so I have decided to take him away to Italy just the two of us.
My sister is 21 on the same weekend and has arranged a party. She’s now really upset that I won’t be there and is not talking to me. I understand she’s upset but I have always made an effort to celebrate her past birthdays and took her to London for her 18th and spoiled her. She’s making me feel guilty and now I don’t know if I should re arrange the trip to Italy for the week after (DP won’t mind) or just stick to my original plans and hope she comes round eventually? I can then arrange something separate for just me and my sister to celebrate but right now she’s not talking to me.

OP posts:
Legomania · 05/06/2026 10:16

SnappyQuoter · 05/06/2026 09:42

No, it isn’t. That’s just people copying American movies and trying to make 21st birthdays “a thing.” Most people roll their eyes because the big one here is 18.

Show quote history

21sts were definitely a big deal in the UK when I and my friends turned 21, 20+ years ago

OneNewEagle · 05/06/2026 10:16

21st is the big one. I would go to my sisters party then out for lunch with my dp for his birthday. Try to do both.

my future MIL hijacked my DP’s 40th and completely ruined it for me. She wanted to take him and his sister and DN for a meal I said a different day over the weekend as I had planned something. She booked it for the time I said and they all went for a meal….I wasn’t invited. She’s ruined a lot of things over the years but to not even invite me.

rainbowstardrops · 05/06/2026 10:16

I don’t blame her for being upset! Why on earth did you book a trip away when you knew it was her 21st?
Your sister is upset and can’t just rearrange a party but your partner isn’t fussed and would happily change the trip away. It’s a no brainer surely?

TheJuicyLucy · 05/06/2026 10:16

I'd want to be with whoever was not guilt-tripping or trying to manipulate me. In your case, that seems to be your partner.

Whatwerewetalkingabout · 05/06/2026 10:16

Well I would say if the 40th trip can be easily postponed without costing a bomb and your partner doesn't mind, I'd do that. I think your sister is being a bit out of order giving you the silent treatment but she's 20, immature and big birthdays tend to mean more to young people, so she gets a slight pass.

However didn't you anticipate the clash? Especially if your DP isn't bothered about making a fuss about his birthday (or at least celebrating it on his birthday weekend) I would have probably checked my sisters plans for her 21st before booking.

Sanch1 · 05/06/2026 10:16

If I was you knowing it was a milestone birthday for her too I would have asked her before booking Italy if she had any plans for her birthday, then it would have been easier to come to a compromise to keep both people happy.

However, as you now can't come to her party, she is being a little bit precious and unreasonable, and as other posters have said she needs to grow up and realise all doesn't revolve around her and you not being there isn't the end of the world.

Moveoverdarlin · 05/06/2026 10:17

Bit weird that you booked the trip, knowing it was the weekend of her 21st. I would have checked first.

Your DP doesn’t seem fussed either way so I would change it.

Tink3rbell30 · 05/06/2026 10:18

Rearrange the weekend, seems simple.

Stickytreacle · 05/06/2026 10:18

Your sister needs to grow up and start behaving like an adult. The world doesn't stop because it's somebody's birthday, and celebrating with your husband on his birthday is to be expected.
I'd continue with your plans as they are, if she chooses to take offence it's her decision.

kkneat · 05/06/2026 10:19

I’d change my weekend away then you can do both. My sister would be very disappointed if I missed her party

Whatwerewetalkingabout · 05/06/2026 10:19

OneNewEagle · 05/06/2026 10:16

21st is the big one. I would go to my sisters party then out for lunch with my dp for his birthday. Try to do both.

my future MIL hijacked my DP’s 40th and completely ruined it for me. She wanted to take him and his sister and DN for a meal I said a different day over the weekend as I had planned something. She booked it for the time I said and they all went for a meal….I wasn’t invited. She’s ruined a lot of things over the years but to not even invite me.

I'd be rethinking the marriage. Why didn't your fiancé stick up for spending time with you on his 40th birthday?

ForeverPombear · 05/06/2026 10:21

SnappyQuoter · 05/06/2026 09:42

No, it isn’t. That’s just people copying American movies and trying to make 21st birthdays “a thing.” Most people roll their eyes because the big one here is 18.

Show quote history

I'm UK, mid 30's and 18/21st birthdays were always a big deal for everyone growing up. It was for my Mum as well, who is hitting 70.

WildLeader · 05/06/2026 10:21

Oh fgs, your sister is being ridiculous @EzWin2

she’s only just planning something now, and will have to accept that not everyone can be there. It’s your H Big 40, that kind of trumps every thing!

fwiw, this scenario won’t ever happen again, as her next big event will be her 30th, and your H will have his next Big Birthday the following year.

sometimes your H gets put first, you get put first and you get to go to Lake Como

xOlive · 05/06/2026 10:22

Is everyone okay this morning?
Since when are we cancelling pre-booked holidays with our partners/husbands for our siblings?
Would you all have the same opinion if OP’s children were going on this holiday? Would you encourage her to cancel/rearrange her family holiday for her little sister?

Your sister is behaving like an entitled brat. Giving you the silent treatment because you’re celebrating your partner’s milestone birthday instead of attending her party that she only told you about last week? Ridiculous and very immature.

Keep the holiday OP.

Nosleepforthismum · 05/06/2026 10:24

Well I can’t even remember what I did for my 21st or who came or even what any of my friends did. It was only 15 years ago! I would prioritise your DP’s 40th because it’s only every 10 years that you get a proper excuse to be spoiled and break away from the drudgery of kids/work and being a grown up. Your sister is being selfish because she’s young and doesn’t properly understand. Hold firm and just say you are sad that you are missing it but you are looking forward to catching up when you get back. She’ll get over it.

taybert · 05/06/2026 10:25

Sister shouldn’t be giving you the silent treatment, it’s childish and unhelpful. That said, having had a sister for 20 years and the same partner for 11 years, I think it probably isn’t unreasonable to expect the situation of two milestone birthdays together would have been anticipated and then perhaps discussed before a weekend away was booked. Especially as your partner is pretty relaxed, it sounds like the party and the weekend away could’ve been arranged on separate dates with a bit of forethought. Asking your sister “Are you planning anything for your birthday before I book DP’s weekend away?” Would’ve prevented the upset.

ALotofThingsBeataJet2HolidayActually · 05/06/2026 10:26

Your sister is being unreasonable. She's only 20 so still has a lot of growing up to do and she's demonstrated this perfectly.

The husband takes priority here. And would you really want to spend an evening with a bunch of 20/21 year olds screaming, crying, getting drunk and probably falling out with each other in the toilets?

The 40th in Italy is much more appealing.

ExitPursuedByABare · 05/06/2026 10:27

Maybe it wasn’t a great idea to book her birthday weekend away knowing your partner isn’t that fussed. You could have celebrated his birthday on the day with a meal out or his favourite cake at home. But it’s been booked for ages, presume she knew you were going (?) p, so I wouldn’t change it now.

Goodmorningeveryone26 · 05/06/2026 10:28

If you can easily change the Italy weekend (and your partner fortunately is acting like a grown up and doesn’t mind which weekend you go) then I would do it, seeing it obviously mattes to your sister. It’s nice she wants you there

JuneAlready · 05/06/2026 10:30

stealthninjamum · 05/06/2026 09:38

I think you should’ve asked her if she had plans before booking the trip with your dh. She’s being childish and not reacting well but I would be upset that you couldn’t be bothered to send a simple text message.

Why? It's his birthday too. Should his always be sidelined for her sister?

Savvysix1984 · 05/06/2026 10:35

xOlive · 05/06/2026 10:22

Is everyone okay this morning?
Since when are we cancelling pre-booked holidays with our partners/husbands for our siblings?
Would you all have the same opinion if OP’s children were going on this holiday? Would you encourage her to cancel/rearrange her family holiday for her little sister?

Your sister is behaving like an entitled brat. Giving you the silent treatment because you’re celebrating your partner’s milestone birthday instead of attending her party that she only told you about last week? Ridiculous and very immature.

Keep the holiday OP.

I just wouldn’t have booked for that weekend knowing it was my sisters big birthday. I wouldve checked first. I love my sister dearly and wouldn’t wanted to have missed a party! I would then have booked an alternative weekend for my Dh and made it a proper surprise- tell him on his actual birthday then go away the next weekend.

Dh could have a whole weekend to himself for his 50th when it didn’t clash with my sisters.

andfinallyhereweare · 05/06/2026 10:36

I would have booked the weekend away for another weekend if I knew it was my sisters bday and my Dp was g fussed about celebrating on the day. Why split yourself in two when there was an easy solution?

titchy · 05/06/2026 10:37

Can you imagine the responses if someone posted ‘My birthday is the same as dp’s sister’s, and every year he chooses her birthday over mine. He even rearranged a trip abroad to celebrate my milestone birthday so he could go to a party she’d only arranged the week before’

BelleEpoque27 · 05/06/2026 10:37

21st isn't a big birthday - nothing legally changes, it's just another year. I know it used to be when my parents were young, but someone turning 21 now is 50+ years past that change in the law! I turned 21 in the early 2000s and it was no big deal, 18 is the big one. I would also think it's unusual to have a family party at 21, doesn't she want to be with her mates?

If your partner genuinely wouldn't mind then change the weekend of your trip and do both, but she is being silly.

JLou08 · 05/06/2026 10:38

I think it was a shitty thing for you to do. Your partner wasn't bothered about his birthday. I'm coming up to 40 and been having friends turn 40 over the last few years, although it is a milestone birthday, none of us have cared about it as much as we did our 21st. Birthday's are generally a lot more important to young people, it's very clear from your post that it is that way with your DP and sister. Your DP isn't bothered, it is very important to your sister, so why did you book something for your DP and miss your sisters party?