Oh gosh, I sympathise.
My father did this 15 years ago. It still hurts.
Huge, Edwardian, 4 bedroom detached house in naice area, with massive garden, employed and then instated as director of the family business after he paid for two degrees neither of which she did anything with, whilst I had to fund my own modest property, a fraction the size of hers, and scrimp and save to pay for additional degree some 12 years later as I was still working for a pittance (after returning from overseas).
I was never told, well in fact I was lied to, she was “just staying there short term” until I asked directly and very politely as I was sick of being treated like a fool and quite frankly the house hurt, but the lies hurt more. Then there was a whole lot of how dare I ask and it’s none of my business and blah blah ie guilt talk.
He’s never met my children, his choice not mine, and I still live in the hope that he will decide to get back in touch and say, “I love you.” Not even “I am sorry.” Or “How are your kids?” Though of course those would be nice.
Ironic really as all he ever said about her was how childish, lacking in empathy, selfish and spoilt she was. Hrm I wonder why.
Note - yes she is a half sibling. My mother died when I was a young teen, and the worst thing of all, I have no idea what happened to my mementos of her or the gifts she bought for me as a child, such as dinner service etc.
Parents are sometimes awful. I’m so sorry that you are feeling this.
I have two children and I could NEVER treat them with such disparity.