Unlike the VM-Host affinity rules, the inter-virtual machine (VM-VM) affinity rules can work between individual VMs.
The following procedure will help you create an Inter-VM affinity/Anti-affinity rule.
From the vCenter's inventory home, navigate to the Hosts and Clusters view.
Select the cluster and navigate to Manage | Settings | DRS Rules and click on Add… to bring up the Create DRS Rule window.
In the Create DRS Rule window, supply a name for the rule, and choose the rule type. In this example, we have selected the rule Separate Virtual Machines. If you intend to keep the VMs together then select the rule Keep Virtual Machines Together.
With the rule selected, click on the Add… button to bring-up the Add Rule Member window.
In the Add Rule Member window, select the VMs to be added and click on OK.
The Create DRS Rule window should now list the VMs added as to-be members which would participate in the rule. Click on OK to create...