u/Dry_Quality_8830

My twin sister and I (both 17, turning 18 at the end of the month) are having a shared family birthday celebration.

I originally had plans to spend that weekend with my boyfriend, but I cancelled because my family was only available that weekend and I didn’t want to make everyone reschedule. Since we share the same birthday, I thought it made sense to prioritize celebrating together with family.
The problem is with my sister’s boyfriend. He was supposed to stay at our house from April 29 to May 12, but he has a habit of never leaving when he says he will. What’s supposed to be a short visit often gets extended without anyone really being asked.

Yesterday, my dad and I realized he was supposed to leave that evening, but when I asked my sister about it, she casually told me he wasn’t leaving after all and would actually be staying through our birthday. Neither my parents nor I had been asked about this.

This is especially frustrating because my brother and sister-in-law are coming for our birthday, and one of us has to give up our bedroom so they can sleep comfortably. My sister-in-law has health issues that make this important, so of course one of us needs to make room.

The issue is that I’ve already given up my room multiple times when family visits, especially when my sister’s boyfriend has been here. I’ve slept on the couch for multiple nights without complaining. The one recent time my sister gave up her room, she complained about it and stayed up on the phone all night, which kept me awake.

Now my sister is basically saying that because she gave up her room once, it’s automatically my turn again. She’s also acting like her boyfriend staying through our birthday is already decided, even though it affects the whole household and it’s my birthday too.

What upsets me most is not even that she wants him there. I understand wanting your partner with you for an important milestone like turning 18. What hurts is that she made this decision without asking me or my parents, especially after I already gave up my own birthday plans to make the family celebration work.

I feel like I have no say in my own birthday, and I’m frustrated that this keeps becoming a pattern where his presence is just forced on everyone.

How do I handle this without causing a huge fight?

We will call my sister L.
Our birthday that is at the end of the month (we’re both f17, turning 18). I was supposed to go to my boyfriend’s place to celebrate it, and since we actually share the same birthday, I thought it would be cute to spend it together. But my family is only available on the weekend of my birthday, which is the exact weekend I wouldn’t have been there.
To avoid inconveniencing everyone and having to reschedule the gathering, I decided to cancel my plans with my boyfriend so we could celebrate together as a family.

My sister’s boyfriend, who we’ll call N, was supposed to stay from April 29th to May 12th, which already feels like a pretty long stay to me, especially considering he never respects the dates he says he’ll leave. When he says he’s staying for two weeks, it turns into two months; one week somehow becomes another whole month... (which is honestly really annoying, especially since he never stops complaining about having no money even though he’s constantly changing his train tickets and ordering food when my mom cooks like crazy every single day.)

Yesterday, around 5:50 p.m., my dad and I realized that N was supposed to leave that very evening, and that we thought he had missed his 5:30 train. I went to see L, a little pissed because he would miss his train again, and she calmly told me that actually, without telling or asking anyone, N wasn’t leaving on the 12th after all. Of course my parents were pissed.

For our birthday, my brother and sister-in-law are coming, and one of us has to free up a bedroom for them so they can sleep comfortably, especially since my sister-in-law has epilepsy and sleep apnea and we want her to be as comfortable as possible.

The last few times they came over, N was always there, so I never said anything. I gave up my room and slept on the couch for probably a total of around 10 nights without ever complaining. And that happened five times in a row.
The last time they came, sometime in April, since N wasnt there, my sister "agreed" to give up her room. She spent like 2 nights on the couch and i could hear her on the phone talking to her bf all night volume all the way up, which kept me from sleeping.

When my mom explained to L that one of the two bedrooms obviously had to be given up, and that my sister and I needed to figure it out together, she and her boyfriend still hadn’t agreed on a departure date. Since I could already see where this was going, I asked her whether she planned to actually choose a date for N to leave, or if she was just going to force his presence on us until our birthday.
Obviously, she told me I had no choice because first, the last time she was the one who gave up her room, so now it was supposedly my turn, even though i did it like 5 times in a row? and second, that N was staying until our birthday anyway (without even asking for permission), which meant her room “wouldn’t be available.”

She says N can’t leave before the end of may because apparently his mother won’t be home until then, therefore wouldn’t be able to pick him up at the train station even though he could walk, take the bus or drive there. And since he’d supposedly be unable to go home until the end of may anyway (right before our birthday), she says he might as well stay until our birthday, something both my dad and I are completely against.

Personally, I think he should have stuck to the dates he originally gave. And honestly, I don’t think he has any place at our birthday at all. In my opinion, their relationship is way too recent for him to be invited to OUR birthday, especially considering this is just as much my birthday as it is hers, so my opinion should matter too.
I gave up on doing things i planed on doing because i didnt want to be a inconvinience to anyone, and now have to spend "my" birthday with someone i barely know. I know its my choice not to go to my bf's place, just because i cancelled my plans doesnt mean she has to do the same, however it feels upsetting that she didnt even ask for my opinion, nor my family's and that it originally wasnt even planned AT ALL and we cannot afford another mouth to feed.
I dont like not even having a say in this.

Before you say its weird that im okay with my sister in law coming but not with N, she wasnt 'invited" to past birthdays (exept my brothers bd of course) until we felt comfortable with her being there. If we didnt share a birthday, of course she could bring who tf she wants as long as my parents are okay, but since we share a day, i feel like we should both consider each others opinion.

I’m not going to buy tickets and go to my boyfriend’s place because I don’t want to spend my 18th birthday upset and away from my family because of all this. I’m just tired of her constantly forcing his presence on us for months at a time while my parents do absolutely nothing about it.
I understand that it is pleasing to have the person you love being with you for such an important moment, its mainly the fact she did not ask beforehand that's pissing me off. Otherwise, we (and I) would've probably said yes.
Im upset she didnt ask and is not giving us, me, a choice even though it is also my birthday.

i do not know if i am in the wrong for thinking this, or being selfish, please help me out on this.

WARNING : I do not care about what you have to say about the age gap, it is none of my business and i dont want to hear what you have to say about it. Please do not bring it up or make any comments about it even though i might agree, its out of topic.

TL;DR: My twin sister and I are turning 18 at the end of the month and share the same birthday celebration. I cancelled plans with my boyfriend so we could celebrate with family, but my sister decided on her own to extend her boyfriend’s stay without telling or asking anyone, even though he was supposed to leave yesterday. She’s now saying he’ll stay through our birthday, which means I’ll likely have to give up my room again for visiting family, even though I’ve done it multiple times before while she only did it once. What upsets me most is that she made this decision without asking me or my parents, even though it’s my birthday too. I’m not mad that she wants him there, I’m upset that she forced this on everyone and is acting like I have no say.
Am I being selfish for feeling hurt and frustrated about this?