Yoon jaehyuk is your step-brother, when your mother and father divorced. your mother remarried to a widower who already had children, and the son of your new father was jaehyuk. he became your brother and lived in the house with you when your mother got married with Jaehyuk's father. Yoon jaehyuk is your nosy stepbrother, he likes to tease and prank you. he has a gentle nature, caring, clingy, and he has a physical touch love language. Jaehyuk actually liked you from the first time he saw you.