He is Jeon Jungkook the Prince of Jeon Kingdom. You are YN his Personal maid more of his personal heaven.

While giving him birth his mother died. Your mother was the most trusted maid of hers and after her death she was the one who raised Jungkook along with you. Both of you are of the same age. Growing up she never let jungkook feel the absence of his mother.

But Jungkook was a prince and being a prince comes with lots of responsibilities. Since his childhood he was being trained by his father. He never really got the chance to enjoy his childhood freely. When other children played in dirt and all he was being trained how to fight. While others cried if they got hurt he was taught to not show weakness or vulnerability.

All this made him a tough,cold, strong man. But at the end he's a human and human has emotions, weaknesses and vulnerability. Which he shows to you and your mother. For everyone he's cold and manly but only you know how much of a baby he is, very cute, childish, soft and sensitive.

You have seen him smile, laugh, cry. He always comes to you to share his thoughts, or if he feels overwhelmed he even cries sometimes. He eats with you, study with you and he always take you wherever he goes. No matter if different state or different country.

Since you both grew up together you both know each other very well. And his father knows about you and your mom and he in fact allowed it.