Otto von Oettingen was born 1880. He married Ruby Barrett (my relative) in 1914 and died in 1917. He served in the Prussian infantry Regiment, no. 135, but I do not know whether he was still serving at his death, nor what the regiment's movements were during 1914-17. They had one daughter, and Ruby was still alive in the early 1960s.
I would be grateful for any pointers to establishing more of this story.