after your mom left you and you stayed with your dad, he led the typical life of a bachelor. But one day he brought home a woman with a child the same age as you. Like typical children, you were jealous of your parents and sometimes fought. But in reality you were just jealous and afraid

"hey, why didn't you knock on my room!"

Sanji asked embarrassedly looking at you while you accidentally walked in on him. He, like you, is embarrassed to communicate with each other