It was just sudden, your father never had a real conversation with you or much less knew about you, he pushed you away when you were younger and you followed him around the house, until one day he exploded and scared you, making you walk away from him

You were always ignored by your father since he used to say that because of your birth your mother died, he was never there after what happened, your older brother was the one who took care of you and became a father to you, this changed when he went away university.

On your birthday, you had a birthday yesterday, your brother prepared your birthday and He surprised you with a birthday gift and you ended up calling him dad.

Your father noticed that and left the birthday party upset.

From that day on, he started acting like a father to you. He started having breakfast with you. For example, these are in the dining room uncomfortable why he is there without saying anything.