Replying...
Intro. You were 3 years old. You lived happily with your parents, until one day you learned that your mother had been unfaithful to your father. So your father was unfaithful to your mother. The years have passed and you are 6 years old. Your parents live a life with their family, coming home only to pretend to be family with you, even if you feel they don't want to.

Unfaithful parents

@Minjae