My uncle had one daughter, as far as I was aware. Aged about 30, at a family party, I was informed that my cousins A, B and C would be attending - I asked who the hell they were as I didn't have any cousins named A, B and C. It turned out I did - they were my uncle's children and his daughter was actually his stepdaughter, who he'd taken on as his own as a baby. When I met these cousins we had friendly conversations where I expressed amazement that I'd never met them or known about them, and they were very clear that this was because they'd fallen out with their father and kept their distance for well over 20 years by now. I repeat, they were very clear that they hadn't seen him once in all that time.
A few months later the same uncle was dying. He went into hospital and then a hospice. For years the daughter I knew had been looking after him and it was understood that she would inherit his house and a reasonable amount of money - she was wealthy and didn't need it particularly, but under the circumstances she was by default his only child.
While he was in hospital the other three turned up to visit him a few times and I started to hear about how close they all were, how he remembered enjoying fishing trips with A, B and C regularly over the last few years and told people how well they'd looked after him. My dying uncle really wasn't all there at this point. A couple of months later he was dead and his will had been changed to leave the bulk of his estate to cousins A, B and C.
The rest of the family seemed to have been brainwashed too. When I questioned it they all seemed to agree that everyone had made up about ten years ago and been very close since then. I pointed out that A, B and C had told me less than a year before that they had had no contact with my uncle for decades, and that was their explanation for why I had never met them. I was met with a lot of confusion and shaking heads. It seemed everyone was pleased A, B and C were back in the family fold, so to speak, and were prepared to overlook the bullshit. In front of people I questioned A, B and C about it and they said I must have misremembered my meeting with them and insisted they'd been around plenty over the last few years. I even asked what was their explanation then for the fact I had never met them until a year ago, and of course they didn't have one but no-one else wanted to challenge them about their lies.
I realise my uncle was entitled to distribute his estate however he wanted to, but this seemed to me a very clear case of manipulation of someone not in a fit state to understand what was going on. These cousins have been around a fair bit since then and I seem to be the only one who is suspicious of them and can't quite accept them.