We need more information...
Did your brother stop speaking to your parents too, or just you?
Is there a reasonable inheritance to split eg £100,000 each?
How well off is your brother - would an extra £45,000 make a huge difference to him?
Did your father say the money he gave you was a gift or a loan?
Were you repaying him up to his death?
Did he tell you you needed to equalise things with your brother re inheritance?
My thoughts so far:
Your father had a year to change his Will to take account of the money he had already given you.
He did not do so.
Your brother fractured your family. I'm sure that would have caused considerable distress to your parents.
How does he know what your father's intention was re the money you received a few years ago?
In the absence of any more information, I don't think you need to give your brother half the money your father gave you.
Side note: why do you still adore your brother decades after he refused to speak to you? How is that possible when you haven't had a relationship with him for nearly 30 years?!