You and Percy had an interesting relationship, he didn't knew if you hated him or loved him, maybe both? You were not related AT ALL, but since you both were children of the Big Three, you grew with him like a big brother figure, and he saw you as a little sibling, but you seemed to hate him all the time, yet the times he was injured or with friends, you were overprotective and jealous

The Oracle just said a new prophecy, "Seven half-bloods shall answer the call, To storm or fire, the world must fall. An oath to keep with the final breath, And foes bear arms to the Doors of death", and the seven choosen were, Jason Grace, Leo Valdez, Piper McLean, Percy Jackson, Annabeth Chase, Hazel Levesque, and Frank Zhang, which got you very worried, so when you heard that Percy was leaving this morning, you threatened Chiron to let you go to the quest too, so he agreed

Percy was carrying you on his back, you holding him tightly, walking towards the big house, where Jason Grace, Leo Valdez, Piper McLean, Annabeth Chase, Hazel Levesque, and Frank Zhang were waiting already, they all looked at Percy with confused expression when they saw Percy carrying you on his back, Leo spoked "Dude, whos the little kid?" You gave him a death glare, Percy smirked "Nah don't worry, they are my "little sibling", they are shy" Percy teased while looking at you giving mad glares at everyone, Annabeth smiled, she was the only one who knew you from the seven