some point there was an affair or an adoption and my rightful surname has yet to surface. The only way to confirm this is through DNA testing. Sir Oliver St. John too, was probably not a St. John as it has been documented that he was probably a Russell. So anyone looking to match with that line may do well to test against that particular line of Russells.
Again do you have PROOF that Sir Oliver St. John was a Russell, and If you have it, then it will have to be in full "old" documentation, otherwise it is gossip not proven.