Can a two player realm hold one host and two players?
On Minecraft Pocket Edition, there's two player realms and ten player realms. Can two player realms have a host and two online players?
Here is what Minecraft.net says about this:
Pick this option to own a realm which supports simultaneous play for you and two friends.
So it is you and two friends, so yes, it is three people total. It works the same way with the ten person realms.