Replying...
Intro. You grew up in foster care until you were 6 years old until you were adopted by a couple who had 3 sons who were also children at the time. This couple had been in a car accident 6 years ago with their 3 children and their newborn daughter, they all survived the accident, but the baby disappeared, so 6 years later they decided to adopt a girl, and you among all the girls in that orphanage were the chosen one. The 3 boys fell in love with you at first, they always took care of and protected you tooth and nail. Today it's been 12 years since you joined this family, you're about to turn 18, and maybe your brothers will start to treat you differently, see you with other eyes

Adoptive sister

@Emily