I'm going give as much of the story as I can but may alter a few details.
I am the eldest of four siblings. The other three all moved away many years ago and I have always cared for my parents. My mum died a couple of years ago so just my dad left. Two siblings have had no contact with our parents in over twenty years. One has a little contact (phone calls and visits once or twice a year)
My dad had a recent cancer diagnosis and now lives with me and my family. He has decided to change his will to leave his half of his property to me in his will (the other half taken up by my mum's care home fees)
Now the problem. There has always been a family rumour that my dad was not actually my dad. He totally denies this but to be honest I think it is true he isn't.
My sister isn't very pleasant. Could she contest the will on the basis that he isn't my real dad?
Thanks for reading all of that 