I get you, it’s happened in my life a lot. And yes sometimes it feels weird and yukky (I wouldn’t dream of doing that to my family).

A partial answer is occasionally it is social exclusion, so a woman maintains her social status in society (or family group). Ie a manipulative and sometimes narcissistic mother in law might sometimes do this. 

You most likely have offended someone by being too beautiful, or too kind, or too funny etc. 

Try not to let these people upset you. 

sd’s are a common one and when you break it down, they have never been taught respect of boundaries, they have been placed into equal wife/aloha female status as the wife of their dad.

Their hcgubm narcissistic pos has taught them abuse and manipulation to get your way is normal. My husband for example cannot have his youngest daughter from ex aged almost 15 because eldest sd24.5 controls her access since bio mum palmed off care to her years ago when they ceased contact

they are just like their mum thinking if they ceased contact that daddy would put his life on hole and jump through hoops. The jumping through hoops did no favours for anyone 

when sd’s started crossing the line by disrespecting pur boundaries and privacy and relaying everyting to bio mum and stepdad vis the interrogation debrief/report, even my 2 children aged 1 & 2.5 were not spared. What we did, where we went, what we spoke or wore...

then sd’s thought they could control and mummy me around, would tell me what they would do to my kids when they were being 100% inappropriate.

at a nephews engagement party they decided to feed my 2 yr old in a white dress melted chocolate that had been sitting in an extremely hot car for 6 hours. It was everywhere when i turned my back for a few seconds to put my son in his seat. All they did was sit there with a smirk.

they’ve even banged on our bedroom door 7am screaming like a banshee wanting special sugar they bought from their aunt in the car whilst we were having sex and our 2 kids were sleeping. They could have waited for their dad to leave the room 30mins later but when bio mum has never respected boundaries well neither do you

final thing is when they manipulate daddy for money. My 24.5 yr old sd has been in fulltime employment since feb last yr. every yr she reminds daddy she needs his $1000 per month to help care for her sister when hubby is paying cs to bio mum... whether bio mum sends all of this to sd who knows because they never disclose anything

i never signed up to be married to a man financially supporting skidults!! As long as that happens we can never have a proper functioning marriage.

i also find it laughable when a sd is placing herself as same league as stepmum... its just disgusting!! Worry about your own sexlife and romantic life and not that of your dad

One of the most common themes on ST is the lack of boundaries, be it BM, our partners and their exes, our partners and their kids, the in laws, etc. When parents don't raise their kids with structure and a respect for boundaries, kids grow up thinking the rules don't apply to them and become manipulative a$$holes running their own agendas; and adults who don't know how to draw and maintain appropriate boundaries end up getting walked over and abused.

Lets be honest - it takes two to kill a marriage/relationship. Most of the parents who are "normal" - functional, well adjusted, come from good family and are good parents - are still in intact relationships, so we come here to vent about the three legged dogs we chose. Many of them come from dysfunctional families and went on to perpetuate that dysfunction. Some were abused and damaged by previous partners. This is why it's so very important to thoroughly, slowly vet the people we date, including observing their family of origin. If I had known then what I know now, I probably would have told my DH to lose my number after attending that first Christmas with his crazy family.

I have learned so much on ST about about my own gender. Females can be a PITA!  Females care about territory and control, whether it's a dynamic, another individual, or both. The ones who grow up without proper boundaries, who don't have engaged mothers and strong fathers willing to check misbehavior and wrongheaded beliefs, learn how to use manipulation and stomp boundaries to get what they want. Many of them constantly test boundaries, looking for that weak spot so they can assert, play their games, and regain that sweet control.

It all comes back to boundaries. If your man isn't able to draw them and enforce them, comes from a family of Godzilla-like boundary stompers, or has an ex and/or kids who won't respect them, your step experience is going to be a rough ride. 

I've not experienced this personally but my aunty is v odd. She shown an almost incestuous interest in her younger brother, his male child and my brother over the years. To the point my cousin was alienated from his own mother and went to live with aunt. My aunt rejected all the wives and girlfriends, none were good enough so she tried to push them out. My brother got it and confronted her during a big bust up at my parents home ten years ago. Aunty left and didn't speak to my brother or her own brother /sil again. then my parents died so never made peace. I honestly think she's got severe mh issues and it's sad as she's only hurting herself. Nobody bothers with her and If she does get invited to anything she tries to make a drama. The latest was my other cousins wedding. Right up to the last minute she was spoiling it for the grooms mum with the 'I probably won't come (beg me to come) my other aunty just turned around and said' you know what dnt come then, stay home be miserable like you are the other 364 a day ' she did turn up but turned her nose up and made spiteful comments about everything 

I have experienced this with my MIL.  She didn't get on at all with DH's first wife, either,  they were daggers drawn the whole marriage. DH is the eldest of 3 brothers and was very close to his mother after his father died when he was about 20.  I get the impression she finds any of her son's wives a threat, but especially my DH's.  We fell out with her badly 2 yrs ago and ended up going no contact. She tried to tell me I wasn't allowed an opinion on a family matter since I wasn't part of the family, although I'd been with DH for 16 yrs at that point!   Since then she has friended NPD BM on Facebook and "likes" and comments on all her posts. Trying to prove she doesn't have a thing about DH's wives, I think.  

I have to admit I acted this way with my brother's now wife. She would have probably said I was jealous but I just thought she wasn't good enough for him. I eventually left it alone because he chose to stay with her so whatever. I still don't think she's good enough for him but I leave it all alone.

I have two middle-aged SD's. They were young when OSD was labelled the pretty one and YSD was labelled the smart one.

I hate labels; I think they limit people. These two sisters were told "this is what you are" and instead of thinking of personal growth.  They still are thinking of ways to outshine each other. Who has a nicer car, whose purse is more expensive, who is aging faster, who is skinnier. Constantly. Given that BM needs constant attention, the apple did not fall far from the tree. 

They are in competition with dad's new SO, but when we are not around they still have other competitions going on. It's pretty sad, really, to need that level of external validation.

I think there is a biological component - thousands of years ago the males hunted and women stayed in the village. Women had to be strategic about getting what they wanted, including attracting a mate, trying to outshine the other women. 

I guess some women of today haven't evolved or done the introspection of "do I feel better being superior to someone else? Does this really make me happy?"

BM used to do this. When I met DH, she was regularly doing things that would require him to drop everything and do what she wanted. As soon as we moved in together, she would regularly call him at the last minute and ask him to do xyz or take the kids immediately. As soon as he started saying "I'll have to ask struggling" she would tell him he was a deadbeat dad who didn't care about his kids, but as he held fast to that boundary, she eventually stopped. For her, it was a control issue. She liked being the person from their relationship who had remarried and could control him because it made her feel superior. It was also a way to stay relevant in his life.

MIL also does this to a degree. She also tries to constantly have secrets with DH or things that are just between them, which I find really weird. What she doesn't know is that DH tells me everything and even puts her on speaker phone for their most tense conversations. I think she is actually a bit of a narcissist, so this is her way to stay relevant. When DH was 24, she told him that he better get married or he'd end up like his "loser" bachelor uncle. DH ran out and married the first person he dated after getting MIL's "advice", leading to 10 years of misery with BM. After DH got divorced, he ended up living with MIL at first and taking care of her, like the "loser" bachelor uncle. I think MIL liked that, despite her proclaiming that, that uncle was a "loser". DH tells me all the time that he thinks his mother was upset when he finally had another serious relationship because she lost out on her companion (DH) and caretaker. She still acts like a hurt child around him, always complaining that he doesn't come around enough, doesn't pay her enough attention, and doesn't do enough for her. This is despite the fact that DH's brother and sister don't pay much attention to her, either. For some reason, DH is the one who is supposed to cater to her. Again, it's about control and relevance for her. She complains all the time that she is alone and lonely, but when her kids are around, she is pushy, doesn't respect their boundaries, or in DH's case, criticizes them, so they avoid her. DH loves to call my mother, because she's friendly, positive, and doesn't treat him like a child, so he feels good after talking to her, as opposed to feeling bad, drained, or taken advantage of, like he does after talking to MIL. If I ever really wanted to get at MIL, I could tell her that DH calls my mother multiple times a week, even when I'm not around. He rarely calls MIL and usually tries to avoid talking to her when she calls.