I am still researching for this post, having discovered only yesterday that Wilfred Owen's cousin Leslie also wrote and published poetry.
Leslie Gunston was the son of Wilfred's aunt - his Mother Susan's sister, Emma E. nee Shaw from Oswestry, Shropshire - and her husband John Gunston, a pork butcher from Holborn, London. Edward Leslie Gunston was born in 1895 in Camberwell, London.
Educated at Kings College, Wimbledon and Kendrick School, Reading, like his now famous cousin, Leslie also wrote poetry and the two found they had a lot in common as they were growing up and sharing holidays. They also apparently had poetry writing competitions between themselves, challenging each other to write poems on a certain subject. According to Dominic Hibberd, Gunston's poem entitled "The End" was published in the YMCA magazine "YMCA Weekly" on 22nd December 1916.
Leslie trained as an architect and was also an extremely talented artist. His work was regularly displayed at art exhibitions. Leslie married Norah Whitwell in 1925.
Leslie died in Hitchin, Hertfordshire in 1988 at the age of 92. His collection "The Nymph, and Other poems" was published by Stockwell in 1917.
Source: Internet Search and Catherine Reilly's "English Poetry of the First World War A Bibliography" (St. Martin's Press, New York, 1978)