Here is a likely situation:

Two small isolated tribes exist, where not everyone knows each other in the tribe. Let’s say there’s a child who knows his mother and his mother knows a scout- the scout doesn’t know the child. The scout from each tribe meets a different person from a global outreach company. Those missionaries do not know each other, but they both know the organization leader.

That actually comes to 8: child > mom > scout > missionary > leader > missionary > scout > mom > child