To not click with boyfriend's sister

[Treetop5456]

We've been together 5 months so far (still new) but i just feel i havent clicked with his sister.
I'm 25 and she's 26 but i find her "bossy",
It always feels like she's having a go at her brother (my boyfriend) for little reasons,
For example,
He got a new job and had to go to an induction day, the day he was supposed to look after his baby sister (who is 15) and her first response was "i have a party that day, what am i supposed to? I cant babysit" rather than congratulation,
Boyfriend's car broke down when he was supposed to be picking up his baby sister (15 yr olds)from his sister's (the 26 yr old's house) about an hour away so he rang sister to let her know and she ranted about how she has a meal to go to and cant believe he cant pick her up,
I was then on the phone to her whilst he was speaking to AA, boyfriend told me to tell his sister to let his 15 yr old sister get the train home (it's a simple train, just straight home, and the train station is next to her house),
She snapped at me and said "im not letting my 15 yr old sister get the train home" and then hung up,
She brought the sister home and had a massive argument with boyfriend.

There's more but i find her a bit much!

I find it interesting that your examples are all of your BF letting his sister down on things he's agreed to do. Sounds like this may well be a pattern with him.

Two examples, each with a 100% solid reason for being unable to help out this time, do not make "a pattern", @Mamboitaliano

Bloke gets a new job. Sister does not even say well done, let alone show any pleasure in his achievement. Instead, she prioritises her wish to attend a party over her brother's career - how was he to know the date of his induction day before he got the job?
The date clash is unfortunate, but any reasonable person would discuss & negotiate solutions - not prioritise their desire to party over their brother's one-off necessity to attend an induction for a new job.

Bloke agrees to give a lift. On route, his car breaks down. He rings to let his sister know - she snaps at his g/f, then after the event, goes to bloke's home with the express purpose of manufacturing a "massive argument".
Who does that? - blames someone for their car breaking down on the way to do them a favour?

My older 2 have a "baby" sister 10 years younger. It is not their job to look after her as they are not her parents. Sounds like your BF is having trouble doing "family break up" and becoming an independent adult.

My DH has a sister a year younger than him. She was so used to him looking out for her that when we went anywhere as 2 families she expected us to defer to her over everything. 20 odd years later she still hasn't forgiven me for stealing her brother but he just ignores her histrionics.

(The word you’re looking for is ‘youngest’.)

No, the word she is using, quite correctly, is 'younger.'

It's just interesting that the 'unreasonable' behaviour in the OP is all about the sister having to take on more responsibility for her younger sister due to the brother. I'm sure I'm not the only one that's seen this happen in families, where big sister is expected to pick up the slack. It just makes me wonder if these are the first two times he's let her down or if it's the kind of continual pattern, where even breaking down then aggravates the sister, with a feeling of 'Here we go again!'

Well, Dragonembroidery does seem to have their own axe to grind here but just to pick up on this:

Also girlfriends come and go but siblings are family forever.

Um, very much not, in my experience - what actually happens is that girlfriends turn into partners/wives, and become the new nuclear family, and once that happens, the twatty kind of siblings who think they have a free pass to treat you like crap and launch themselves into a pissing competition with girlfriends 'because he's MY brother' are quickly consigned to the 'see you at Christmas if we have a mo!' dustbin.

Nobody likes being pushed around and treated badly. I've never seen this kind of family dynamic survive very long once the downtrodden sibling really starts a life of their own - sibling bonds can be surprisingly weak. Big sis is on borrowed time, and if she's daft enough to start throwing her weight around and pissing off the girlfriends too - oof, bye sis.

The word you’re looking for is ‘youngest’

@RedRed9, no. She is correct to use the term younger as she is the younger of two.

If there are two, we say older or elder sister and younger sister.

If there are three or more, we use oldest sister and youngest sister.

Brother and sisters argue it's normal as for his sister you don't have to like each other.

@FizzyGreenWater Completely agree, big sis is on borrowed time. At some point something will snap.

I have a couple of older sisters, the eldest is super bossy, she always demanded and condescended, drama queen, everything was always about her & her word was law.....if I dared have an issue or didn't agree with her - all hell would break loose.

I have very slowly distanced myself over the space of 20 years...life is so much nicer without her berating bullshit.

It's just interesting that the 'unreasonable' behaviour in the OP is all about the sister having to take on more responsibility for her younger sister due to the brother.

But of course it is - because we are seeing OP's perspective, & she's not going out with the sister! Having said which, I completely understand your "here we go again" point about gender bias & the domestic slack being picked up by sisters more frequently than brothers.

what actually happens is that girlfriends turn into partners/wives, and become the new nuclear family, and once that happens, the twatty kind of siblings who think they have a free pass to treat you like crap and launch themselves into a pissing competition with girlfriends 'because he's MY brother' are quickly consigned to the 'see you at Christmas if we have a mo!' dustbin Lovely.

Completely agree, big sis is on borrowed time. At some point something will snap
This sounds like the national geographic lions taking over a pride. If older Dsis is bossy blame her parents, okay his 2 let downs had valid reason's this time. After 5 month's I wouldn't make assumptions.
My ex's Dsis was very controlling I thought, it turned he was a bit of a disaster all round, losing jobs, forgetting about occasions, never reliable. She took on mothering him in his teens.

@FizzyGreenWater & @sundaypie yep, 100%!

We don’t see much of my imperious, snide-comment-making, critical, mean, condescending, high-handed, ego-riven sister nowadays

Funny that!

Why does a 15yo need to be minded?

I was babysitting a 2 and 4yo at 15.

Agree with other PP. They do sound like hard work. Why can't the parents pick her up?

Sounds a bit like the Royal Family and poor old "our Anthony" getting put on all the time.