Many thanks for your reply. I think the German adoption is speculation, no one knows for sure.
My grandfather did marry in Ireland in Rathcoole 1928 to my grandmother Rose Kearns. His occupation was recorded as soldier at portobello barracks. I think he was born 1898, but can't find any records of his birth or his parents names. He lived in Rathcoole / Newcastle area from married and had children Fred (my dad), rose, Sheila, Sarah and Theresa. I don't know where he came from prior to his marriage as the barracks is address. Can't find him on the census of 1901/11.He moved to London with daughter Sarah after my grandmother died and I think he died in London I think in 1975. Thanks.