I am confident my sister is a narcissist.
People do complain that MNers bandy it about too much and armchair too much, but honestly, reading about it on here was like having a ginormous weight lifted off my shoulders.
As a child she was PFB and an Only for just that bit Too Long and then got two siblings, one quite poorly, very quickly.
It turned her in to a resentful, spiteful bully. She basically couldn't cope with sharing DM and took it out on siblings and DM. DM made it worse by exploiting the resentment into a Divide And Conquer parenting style which pitted us all as rivals. Her own DM parented rivals so it was learned.
She couldn't cope with any attention or praise we got, anything we were bought, anything we achieved, it was always taken as a direct personal slight, particularly as we were both more academic. It would have to be counteracted with nastiness, usually verbal attacks, really vicious ones, to put me or us back in our place. Spoiling family days if someone else got attention - caused a massive public scene once because a friend of my gran bought ME a present, and then tried to blame it all on me because I cried - though she was much older.
Temper Tantrums of a toddler well into adulthood. And this is where the lying began. Her childhood was spun into a Cinderella story to all her uni friends, including exaggerated poverty, when she was very much the villain. She had a lot of friends at one time, they have fallen away, she is unable to maintain a relationship, and I think she just ends up repeatedly being exposed as a manipulative and spiteful liar. Is a malignant tumour of a person in all honesty. The type to try it on with your DH and then try and convince you he'd tried it on with her.