Exactly half way between the ages of the oldest and youngest
(Kilian - 9, Camille 4 1/2, Genevieve - 0)
Older blond brother and brunette sister AND younger blond brother and brunette sister
I don't know any specifics of "middle child syndrome"
but in your case, it must mean: amazing, fun loving, girlie little ball of sunshine.
May you never get "lost" in this growing family