Share a group calendar with individual in the same organisation

Share a group calendar with individual in the same organisation

I have a group with 4 users. This group has it's own group calendar.
How can I share this group calendar with a 5th user of the same organisation who is not member of this group?
Do I need to add it as member in the group first?
In my case I do not want to add him as member. Can I share it with him (in that case)?