Personalized Big Sister Superhero Youth Long Sleeve T-Shirt. Big Sister Superhero! The big sister looks out for her younger siblings, just like a true superhero should. Great Youth Long Sleeve T-Shirt - White for any super sis! youth long sleeve t-shirt. Shoulder-to-shoulder taping. Youth: S(6/8), M(10/12), L(14/16), XL(18/20)