So Relative! Keep Calm I'm The Big Brother (Black Print) Boys & Kids T-Shirt What kid doesn't love cool t-shirts? Surprise the big brother to be with this fun tee guaranteed to bring smiles to everyone who sees him! This an original design by So Relative!. Read all the bullets below for specific sizing information. These are 100% heavyweight cotton shirts (Sapphire is 90/10 Cotton/Polyester.) They are professionally screenprinted with long-lasting plastisol ink. They do run a little small. Please consider ordering a size up. Youth sizing is as follows: Youth X-Small (2-4); Youth Small (6-8); Youth Medium (10-12); Youth Large (14-16); Youth XL (18-20).