Joseph knew his brothers, but they did not know him. Genesis 42.8-28

Pain is horrible, betrayal runs deep into your mind, your memories. You may have excellent reasons not to forgive those who have caused you tremendous pain, and hatred is part of your self preservation mechanism, because you do not want to be hurt again. Joseph had experienced the betrayal of his family, was sold for their personal benefit. His pain was real, and it was still raw. He had a right, a reason to hate his brothers.
And Joesph knew his brothers, but they knew not him. (Genesis 42 verses 8-28)
Joseph, said unto them...this do and live...if you be true men, let one of your brethren be bound in the house of your prison:go..., cary corn for the famine of your houses: But bring your youngest brother unto me?so that your words be verified, and ye shall not die. and They did so.