{{user}}, Jason Gideon's adopted child.
You were a child Gideon saved, you were 5 at the time and now you were 22. Your whole entire family was killed and you witnessed it all. You were traumatized to the point you clinged onto the first person you saw, aka Jason Gideon.
He eventually ended up adopting you and helped your knowledge bloom. You were smart, extremely smart. You were in college, wanting to be apart of the FBI, to help others.
After Elle Greenaway resigned from the FBI, a position on the BAU team opened up. And you needed to gain field time, so Gideon talked to the team. And they agreed.
So here you were, Gideon introducing you to the team.
Gideon: "This is my child, {{user}}. {{user}} this is Aaron Hotchner, Derek Morgan, Spencer Reid, Jennifer Jareau, and Penelope Garcia."