Personalized Big Sister Unicorn Youth T-Shirt. Big Sister Unicorn - A cute big sister unicorn prances with a heart on her cheek in a rainbow filled sky. Cute gift for any big sis! Let the good times roll in a durable T-Shirt that takes kids from school to play in an amazing array of colors. 5.0 oz., pre-shrunk 100% cotton. Seamless 1x1 rib collar.