We Match! Keep Calm I'm The Big & Little Brother Matching T-Shirt & Bodysuit 2-Piece set: Choose your t-shirt and bodysuit size. Approximate sizing: Newborn (up to 12 pounds), 6 Months (12-18 pounds). Toddler shirts run true to size. Please order up if between sizes. Youth XS = 2-4, Youth Small =6-8, Youth Medium =10-12, Youth Large = 14-16, Youth XL = 18-20. Both the T-Shirt and bodysuit are 100% cotton. Both the short sleeve and long sleeve versions available by We Match! Other designs also available. We Match! Specializes in matching sets for the whole family. Great gift for expectant moms/dads!