Sister super critical of brothers’ partners

[serene8]

I have two brothers and one sister. One brother is married, another has a partner, my sister is in a new relationship, and I’m single.

Over the years, starting around the time my older brother got married, I’ve noticed that my sister tends to be very critical of both my brothers' partners. It feels like she’s always actively looking for something to criticise them over. Even when one of my brothers is at fault, she’ll find a way to blame their partner instead. I find this behaviour odd and honestly exhausting. She’ll go on and on about the smallest things, never directly to my brothers or their partners though, just to anyone who will listen. It’s draining to be around.

It feels like she’s determined to dislike them and constantly looking for reasons to criticise. Like they’re expected to be perfect when she is/we all are far from perfect. Even when they have vulnerable shared something with her, she'll somehow find a way to use it against them in the most warped ways. It’s hard to be on the listening end of what feels like constant unjustified negativity. My mum and I are not like this and have a good relationship with my both. My sister’s relationship with them is polite but sometimes cold and not much depth or interest.

I wonder why she does this. Has anyone experienced anything similar?

My SIL (DH's sister) was like this with me. It seemed as if she was jealous of me, which I found really strange. She wouldn't say anything directly to me if I'd said or done something to upset her - but I'd find out about it much later, usually when MIL complained to DH about it. Sometimes a friend or relative might reveal that SIL complained about me to them, too.

SIL is the kind of person who demands attention, she dominates conversation and has strong opinions - she hates it when other people are assertive about having their say (and I'm an assertive person).

I don't know if there are any similarities with your sister but my advice is not to engage with her bitching and complaining. Don't encourage it, stay neutral, change the subject. Maybe discreetly warn your brothers about it if they are not aware.

I hope your parents don't listen to her too much, as she could poison them against your SILs (which is what my SIL did with my PILs).

I suspected jealousy too. Also mistrust of outsiders, a kind of us verses them mindset.

I’m slowly learning not to engage as I get drawn into defending my SIL’s as I’m dealing with someone who cannot be reasoned with. Her only interest is in criticising them or making them wrong somehow for whatever silly reason. Even when I’ve highlighted the contradiction in blaming my SIL for something my brother has done, she somewhat acknowledges it and goes right back to it being SIL fault.

I didn’t think to warn my brothers as I didn’t want to stir the pot but maybe I should. I am aware they feel a bit of coldness and
lack of interest so probably won’t come as a surprise.

Thankfully my parents don’t. They largely block her out and I need to the same.