His father died in France in 1917 from wounds received in World War I. His uncles were Stephen Shepherd Allen and William Allen, and his grandfather was William Shepherd Allen.
His mother was Elizabeth Penelope Candlish, daughter of John Candlish.
Another son, Colonel Sir Stephen Shepherd Allen, (1882–1964) was a New Zealand lawyer, farmer, local body politician, and Mayor of Morrinsville.
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