I have a family of four. I want to use all family sharing features for 3 of the 4 iPhones in our family. For the 4th iPhone, I want to use some family sharing features while excluding sharing purchases. The reason is that my step son has his own AppleID for purchases separate from the family (his dad pays for his purchases). I am finding little on this type of usage and so far our experience is that an iPhone is either fully IN or fully OUT of family sharing. Any ideas?