Technically this is not possible since VM Protection and replication is a One-to-one site pair operation.
Please consider the alternative solution below:
Query: Replicate VM to third site C prior vm failover from Site A to Site B.
VM replication from Site A to site B.
Deploy Site C with VR and SRM and then pair Site C with Site A.
PS: please clarify if replication between Site A and Site B is using SAN replication or Vsphere Replication.
If using SAN replication between Site A & Site B.
Then just unprotect VM within exiting Protection Group.
PS: please note san replication will keep running in the backend since its Block base replication.
So vm just need to reside within datastore to have to replicate to Site B.
Here you can just configure the Vm replication using vsphere replication between Site A to Site C.
Then as required just perform manual recovery of the replicated vm using vsphere replication to recovery vm in Site C.
Once completed, just stop vm replication in vsphere replication and configure VM protection in SRM in the previous protection group using SAN replication and perform failover when required.
If using vsphere replication:
Here is vm was already replicated and protected:
Please follow steps below:
Unprotect and remove vm within SRM only.
Then go to DR Target datastore and rename vm folder. ( this will retain existing replicated VM data.)
Then just stop vm replication between Site A & Site B.
Once completed, please configure the same vm replication between Site A& Site C.
Once vm has completed sync you can perform manual recovery using vsphere replication to recover VM in Site C.
Once completed, then just stop vm replication between Site A & Site C.
Then again reconfigure VM replication between Site A & Site B, but here use existing seed data so that vm will replication will complete quickly.
Once sync completed configure VM protection In SRM and perform failover when required.
Hope this clarify your request.
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