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AIBU?

Share your dilemmas and get honest opinions from other Mumsnetters.

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:
viques · 05/06/2026 11:05

Your sister is going to turn 21 which means she probably had a special birthday celebration just three years ago when she was 18. Your partner last had a significant birthday ten years ago. So sorry sis, suck it up!

In nine years time you can help her celebrate her 30th. Your partner will have to wait 10years for his next blow out!

Have a terrific time in Italy.

It is also likely that in the next ten years or so your sister will get engaged ( party !) and get married ( hen do!wedding!) or have babies ( gender reveal, baby shower, christening, baby’s first birthday, baby’s first Christmas)so she has lots of celebrations centred around her to look forward to. She can let this one go.

Passingthrough123 · 05/06/2026 11:05

I would not be cancelling a trip booked months ago to Lake Como for my partner's 40th to attend a 21st party where the host will be so busy greeting all the guests and mixing with her friends that she's unlikely to have more than the briefest chat with me on the night.

Do something special with your sister another night. If she continues to be bratty sulk about it, that's on her.

Mumandcarer80 · 05/06/2026 11:05

MeetMeOnTheCorner · 05/06/2026 09:28

You didn’t need to go away and deliberately miss her party! That’s insensitive and why could you not do something on his birthday and go away the following weekend. That’s what mature people would do. I’m not surprised your sister is miffed. So you are being unreasonable.

Exactly this

Passingthrough123 · 05/06/2026 11:06

Mumandcarer80 · 05/06/2026 11:05

Exactly this

Read OP's comments – she booked the trip months ago. Her sister has only just decided to have a party.

Collaborate · 05/06/2026 11:06

She's giving you the silent treatment because you have the nerve to celebrste your husban's watershed birthday with him at the time of his actual birthday and didn't putm her above your husband. I'd respond with the silent treatment until she grows up.

Yikes101 · 05/06/2026 11:06

I’m surprised that you didn’t check with your sister about what celebrations she is planning and when they would likely be before you booked the trip for your partner. We have 7 family birthdays in the same month, we always negotiate who’s having which weekend for any celebrations. If you did and she was vague and then organised her party later then that’s on her.

Slightyamusedandsilly · 05/06/2026 11:11

Of course you're not unreasonable. Get her a lovely gift, and in the card, promise her a day out/meal/event of her choice (or something you can plan for her).

She's being daft if she expects you to throw away hundreds of pounds on something already booked and paid for.

Let her have her tantrum and don't engage with it. She sounds as if she's the over indulged youngest child.

Ponoka7 · 05/06/2026 11:15

Owl55 · 05/06/2026 10:47

Some Young people want everything these days , they want so many birthdays to be special days and it seems to be becoming the norm
13 th
16th
18th
and then expecting the 21 st to be special too !!

These days? It's not that songs about turning 16 have been around for decades. You are 17 going on 18? 18 was because of drinking/debutante balls and joining up, for boys. 21 has always been a massive deal.
OP you should have asked if she had anything planned, especially as your DP wasn't bothered. I'd change the trip.

Nathalie1975 · 05/06/2026 11:16

I wasn't born in the UK and I never understood why 21 is still a big birthday here. Surely 18 and 20 are the big ones?
Anyway, your sister is being ridiculous.

FridayFeelingIsTheBest · 05/06/2026 11:18

I know she has only just told you about the party, but you would have known it’s her 21st before that, so why plan to be away?

My partner would think I’d lost the plot of if booked a holiday to clash with another big birthday for someone I was close to, so he’d say rebook the trip, we’d have a nice meal together on his birthday, go to my sisters party and then go on holiday.

FridayFeelingIsTheBest · 05/06/2026 11:19

Nathalie1975 · 05/06/2026 11:16

I wasn't born in the UK and I never understood why 21 is still a big birthday here. Surely 18 and 20 are the big ones?
Anyway, your sister is being ridiculous.

20 isn’t big here. Surely you understand different countries have different ways of doing things.

Whattodo127845 · 05/06/2026 11:19

Your sister is acting like a child. You can easily do something nice with her when you're back. It's not like this is a new relationship. Go to Italy, have a lovely time and let your spoilt sister sulk.

lemontova · 05/06/2026 11:21

She's seeing this as you choosing your partner over her, which feels unfair as the world revolves around you at that age. But your partner's birthday hasn't changed date, if it was so important to her that you attend her party, she could have sent round a 'save the date' ages ago. Say you're sorry you can't be there and bring her back something nice from Italy. Have a lovely weekend celebrating with your partner!

SheDoesntEvenGoHerex · 05/06/2026 11:22

She's perfectly fine to be upset you will miss it but if she had no solid plans in place, you were free to go ahead and book your trip away!

If she had said all along 'I'm having a 21st Birthday Party' ...you know when her birthday is so YABU to book something and go away, you could have done another weekend with DH who sounds quite relaxed.

However, if she's not mentioned anything about a party or nothing has been booked, then she could have been doing something with friends, with her boyfriend, girlfriends, anything! Were you supposed to keep that weekend free 'just incase' I don't think so.

She will get over it OP. Have a lovely time in Italy!

ILoveRichardOsman · 05/06/2026 11:23

Ellie1015 · 05/06/2026 10:14

I am mid 40s and 21st was a bigger event when I was 21. Definitely not to do with America. Often 18th parties are difficult as most places wont hire for 18th where I am as there will be too many under age guests likely to try and drink. Party for 21st much more common.

Appreciate it may not be that way all over but absolutely the way it is in some places.

Same age and agree totally. 21st was a much bigger event due to the fact we could all go out drinking and clubbing and not have to worry about under age friends, I remember having to sit in car in a night club car park once for my friends 18th as the bouncers wouldn't let me flirt my way in as they usuallly did! It was to obviously an 18th there was another 17year old with me and our friends kept coming out to check on us and give us glow sticks 😂!. My 21st was an awesome night out. It was definitely nothing to do with US influences as we were much less influenced by them then, social media was new.

Op I think you should feel a little guilty as you must have been aware when booking Italy that it may clash with your sisters potential plans. However, your sister also sounds ridiculous so I'd go with your partner due to the expense of changing and just apologise again to your silly little sister, I'm sure she will come round eventually.

HumberSquid · 05/06/2026 11:23

Ellie1015 · 05/06/2026 09:40

I am in the UK and 21st definitely a big birthday. Must vary within UK too.

Well Im also in the UK and dont know anyone that celebrates 21 any more. Its 18 when you become an adult, what changes at 21?

Nathalie1975 · 05/06/2026 11:24

FridayFeelingIsTheBest · 05/06/2026 11:19

20 isn’t big here. Surely you understand different countries have different ways of doing things.

Yes of course but why is 21 still a big one when nothing special happens at 21 now? 20 makes more sense as it's a change of decade.

menopause59 · 05/06/2026 11:24

I think it depends on timing of it all, if your holiday was booked before her party then she is being unreasonable but if you knew she was having a party and then went and booked your holiday, you are being unreasonable especially as your DP is not bothered when you go on holiday.

Evilspiritgin · 05/06/2026 11:25

21st are still big in my area of the uk ,

who’s looking after your children that weekend ? If it’s your mum, I wonder if that’s why she’s a tad more upset

menopause59 · 05/06/2026 11:26

HumberSquid · 05/06/2026 11:23

Well Im also in the UK and dont know anyone that celebrates 21 any more. Its 18 when you become an adult, what changes at 21?

My daughter had a party this year for her 21st cost us a small fortune people do celebrate

Tableforjoan · 05/06/2026 11:27

Honestly I wouldn’t move a holiday for a party.

You booked it first and also the silent treatment would just piss me off she’s going to be 21 she’s an adult.

Id of offered to do something together the weekend after or before but with her grumpy arse she’s get a card and gift 🤷🏻‍♀️

Nannyfannybanny · 05/06/2026 11:27

People "became of age" ie, 18 in January 1970,so for 55 years 21 is just a year. Go with your partner and enjoy.

Onelifeonly · 05/06/2026 11:28

I can't judge if YABU or not. Would you normally celebrate with your sister on her birthday? Did you wonder what she might have planned for her 21st? Is she someone you would expect to want a party? How many people are invited - your absence may be less noticeable in a large crowd?

I don't think a 21st is necessarily more important than a 40th. It's a personal matter. (I felt unwell on my 21st and was hoping everybody would leave soon, but had two 40th celebrations.)

I think though that you could do something separately with your sister, as you have suggested and keep the holiday booking. Even if you cancel or postpone it, she might still continue to resent that you didn't think of her. Then no one "wins".

LettuceAndCarrots · 05/06/2026 11:30

Given the holiday was booked ages ago and would be expensive to change, I'd still go on the holiday.

I do think it would have been polite to mention it at the time of booking to your sister though so she could have planned her party for another weekend if she wanted you there that much. But equally, she should have checked you were free.

VisitingSanta · 05/06/2026 11:32

Your sister isn't exactly covering herself in glory here, but it's not like you didnt know when her birthday was when you booked the trip.
What does your husband say about it?
I'd be reluctant to move the trip if it costs a lot, but tbh this is totally on you, poorly planned.