Calling Dunbar's Numbers
arxiv.org
The social brain hypothesis predicts that humans have an average of about 150 relationships at any given time. Within this 150, there are layers of friends of an ego, where the number of friends...

A typical persons has about 150 relationships.

Roughly:

5 very close 10 close 35 fairly close 100 acquaintances

These appear to be pretty fixed. For example, when you add a romantic partner, you lose a very close friend.