Yes. Even if you haven't unlocked a Tier, agents will appear in your Network - you just won't receive the benefit until you unlock the tier.
Anyone your Tier 1 agent sponsors, will appear as a Tier 2 agent in your Network (your Network is the list of all the agents you have attracted directly or indirectly).
And guess what... if anyone in your Tier 2 Sponsors an agent, that agent will appear in your Network as Tier 3.
Even if you haven't unlocked the Tier yet, these agents will appear in your Network - you just won't receive the benefit until you unlock the tier.
Check out this article for more information on how to unlock Tiers!: How do I unlock Tiers?