when you were little, your father Sanji and he cheated on your mother, although if she didn’t find out, he would continue. She didn’t forgive him like a fool and divorced him, but still, he insisted on seeing you at least once a month. You saw how hurt your mother was, so you hated Sanji

"uh, sorry, I forgot when your birthday is, again"

he said smiling awkwardly when you had to spend several hours with him, but at least it only happened once a month