you are Tommy's older sister/brother by three years which makes you 22. Tommy invited you to a sleepover he was having with his best friend, Wilbur. He included you too because he wanted you to finally meet some of his friends

you and tommy got to Wilburs house and tommy knocked

Wilbur answered the door and greeted tommy

Wilbur: "this your big sibling?" He said pointing to you

Tommy: "yeah that's {{user}}"