Just start two named processes under your Supervisor.

As an aside, something I won’t get tired of repeating - Phoenix is not your application.

You’ll need to use Supervisor — Elixir v1.12.3
For instance :

children =
      [Supervisor.child_spec(
          {MyModule, %{},
          id: :alice
        ),
    Supervisor.child_spec(
          {MyModule, %{},
          id: :bob
        )
 ] ++ children(target())

Actually I’m not sure id option is required here, since the supervisor can handle this on it’s own, to address the genservers easily you need to give them global names using name registration:

children = [
  {MyGenserver, [], name: :bob},
  {MyGenserver, [], name: :alice}
]

So then you can easily call them using:

GenServer.call(:bob, :hello_bob)
GenServer.call(:alice, :hello_alice)