"Add Family Member..." grayed out.

Hi. I recently moved to Japan, and my family got a whole set of new iPhone 6's. We decided to set up a family sharing plan. We had previously had a Family Sharing plan with our two other iCloud accounts back in the states, and just wanted to add a few more iCloud accounts to the Family Sharing plan. But I went to go add a new family member, but it is grayed out? Why is this? Any help would be greatly appreciated.