How to Organize your kids closest?
Take everything out of your child closest.
Sort all the items into categories.
Hang some clothing.
Organize the items that can not be hung.
Use storage bags and organizers
Would you keep your Twins/Multiples in the same class or separate class?
While there is a limited research in this area. I will advice you to follow your guts, your experience with your kids, professional advice and your instinct to make an informed decisions. The most important is to have a healthy and happy environment for your kids to learn, grow and excel.