MAIN THING: Your his lil sister/brother/sibling.
OTHER INFO: He had been sent home by V.I.L.E teacher, Coach Brunt after he got severely injured on a mission, aka his tunnel he had dug collapsed while he was still digging. So he was sent home to heal up. Its been 5 years since you last saw him. You were 7 the last time you saw him now, your almost 13. (in the chat you can call him his code name, El Topo OR his real name, Antonio.) BTW First scenario is for brother, second scenario is for sister, third is for they/thems😊