Can you read? DID you read ALL the OP's post? My guess would be "Barely" and "No".
I'll help you out by summarising it in (mostly) words of 2 syllables or less:
OP's "father" (and that is being kind because he certainly didn't act like a father), had an adulterous (sorry, more than 2 syllables there.....) affair and left his wife and child high and dry to be with his mistress. He allowed his own child to live in poverty whilst he enjoyed a nice lifestyle with his new wife snd HER children. He treated his step-children far better than he treated his own child. Fast forward 50 years and after caring for her own mother through her final illness, OP finally has time to build a life of her own. However, "father's" wife is now ill and he isn't in good health either, and to the surprise of no one, his step children, the ones he cherished instead of his own daughter, don't want to know. So who does he expect.to drop everything and jump in to save the day? That's right, that very same daughter that he didnt give a single thought to all those years ago!
So: "Were they so cold hearted in your upbringing?". If you'd been able to read the post properly you would have seen that he abandoned his family and left them in poverty. That seems pretty cold hearted to me.
"You clearly have no feelings of affection, not even a sense of duty". Why should she? Where were HIS feelings of affection or sense of duty when his daughter needed him as a child?
"The only reason you stay in contact at all is for your inheritance". Do you often find yourself adding fictional narratives to other people's experiences? Might want to take a look at that bad habit...
"Have the decency to tell them that so that they can make alternative arrangements in their will". You REALLY think they'll have made ANY provision at for her in their will!?? Are you living in cloud cuckoo land? He wouldn't even support her during her childhood, when it was really needed, you honestly think he's going to bother about her now!?
"You are not the adult, you are the spoilt teenage brat who thinks other people exist merely to be used". Exactly HOW is OP "using" her father? And exactly HOW is she spoilt? HE certainly didn't act in an adult manner when he abandoned her, so why does she have to suddenly act like he's the best thing since sliced bread?
"If my children treated me as you appear to treat your parents, they’d be written out of my will straight away". One would hope that you would not run out on your children when they were dependant on you and vulnerable and refuse to support them! And OP hasn't treated her "parents" in any manner. She treated her MOTHER, the parent who actually ACTED like a parent SHOULD act, extremely well. She cared for her, putting her own life to the side, right to the end. Her "father" doesn't deserve that title and the woman he married is NOT OP's "parent" in any way, shape or form.
You really need to learn to read properly. Then you need to learn to read ALL the information before jumping in with both size nines.....