Personalized Big Sis Girls Cute Sister Announcement Youth Long Sleeve T-Shirt. Big sis Youth Long Sleeve T-Shirt - Royal Blue for a girl has colorful lettering that says BIG SIS with flowered border for a sister. youth long sleeve t-shirt. Shoulder-to-shoulder taping. Youth: S(6/8), M(10/12), L(14/16), XL(18/20)