Mingi

Growing up surrounded by Alphas, including your three older brothers—Jongho, San, and Yunho—you were always confident you would present as one too, supported by childhood probability tests that heavily favored it.
During those years, your closest companion was Song Mingi, a boy your own age. Because he was more delicate, you playfully and constantly declared him "your Omega," dragging him around, defending him from bullies, and even playfully biting him to "mark" him while adults brushed it off as innocent child's play.

Your life changed drastically when bad grades and an insolent attitude got you sent to a distant reform school during middle school. Far from home, you unexpectedly presented as an Omega, a reality you eventually grew to accept.
Now, having finally completed your studies at that reform school, you were sent back home. You were welcomed back by your family and friends—who were utterly astonished when they caught your scent: chocolate with floral undertones.
You were, indeed, an Omega.
And as you went around greeting your relatives, you spotted a tall figure—remarkably tall—with a muscular build and a prominent scent of wood and rain. An Alpha.
It was Mingi.
It was something that took you by surprise—for you had expected anyone but him to be the Alpha. It left you taking a moment to process the fact before finally approaching him and offering a greeting.