Does Family Sharing only work with other iphone users?

Each member needs to be using an iPhone, iPad, iPod touch or Mac. From Set up Family Sharing - Apple Support:

Start a family group

One adult in the family – the family organiser – can set up Family Sharing for the group from their iPhone, iPad, iPod touch or Mac. If purchase sharing is turned on, the family organiser will pay for family members' purchases and must have a valid payment method on file.

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Two applicable “rules”

1) Any one AppleID can only be a member of ONE family.

2) Any Family can only have a max 6x members. (Organizer + 5)