Interested in your message. I have been trying to trace my ancestors too, but with no luck. I seemed to have hit a brick wall. Perhaps you might be able to help. My father was called Edward Patrick Kerstin born in Londonderry 19/01/27 d 19/11/81. His father was Edward Ernest Alexander Kerstein born in Bermuda 19/09/03 d 19/07/78. His father was called Edward Kerstein. He was a Captain in the British Army. Married a Margaret Corbett d 13/07/60 aged 80.
It is known within the family that the name was changed at the turn of last century because it sounded too Germanic. It is rumoured that the family lived in Prussia and was exiled to the salt mines in Russia by one of the Tsar and two members managed to escape through Scandinavia and made their way to England. From there they moved to Ireland.
This is obviously not directly connected with your immediate family but I would be interested to know if there is a distant connection.