Creating a minimum number of item to select when a particular item is chosen in store.

Hey! 

I run a kid's clothing shop that carries multiple sizes, and multiple items (shoes, shirts, pants, etc.). I'm trying to figure out a way to list onesies BUT also have them require a minimum add of 3 to any order.  Since they're differently listed items, i'm not so sure if that's even possible. 

Anyone done this before?