This KB article explains how to add a Site Recovery Manager (SRM) site pair with a custom extension to an existing vCenter Server deployment already utilizing an SRM site pair with the default .vcDr extension.
For example:
VC A --------- VC B --> vCenterSRM A1 --------- SRM B1 --> Existing pair with .vcDr extensionSRM A2 --------- SRM B2 --> Custom extension site pair
VMware Live Site Recovery
Follow below steps to configure additional SRM site pairs -