So Relative! Keep Calm I'm The Big Brother Baby-Boys, Toddler & Kids T-Shirt Riverstone Goods is the only authentic manufacturer of this item. If the item you are purchasing does not say "Sold by Riverstone Goods" they are not guranteed to be authentic and/or high quality. 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 (Sport Grey, Vintage Red & Vintage Royal are 90/10 Cotton/Polyester.) They are professionally screenprinted with environmentally-friendly waterbased ink. Youth sizes do run a little small. Please consider ordering a size up. Toddler sizes available are 2,3,4 and 5/6. 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).