i have a vCenter and two hosts.
I want to replicate servers from host 1 to host 2.
Is this possible with vSphere Replication with this scenario?
Based on your title "
you can't vsphere replicate a vcenter server.
Based on your actual posts, sure that will work you don't need separate centers, but you do need vcenter to recover the vms(yes you may see stuff out there saying you can without vcenter but its problematic and shouldn't be used at all.
If the question is to replicate VMs within single vCenter server, yes you can do that. Ensure VMs are replicated to different datastore than the one where the original VM is running.
Please refer following documentation --> Replicating a Virtual Machine in a Single vCenter Server Instance