William Joseph Brett
- Born: Abt 1831, Islington, London
- Marriage (1): Sarah Imison on 25 May 1857 in St John, Hoxton
- Marriage (2): Mary Ann Cornwall on 7 Oct 1878 in St James the Great, Bethnal Green
- Died: Q4 1904, Shoreditch, Middlesex aged about 73
William married Sarah Imison, daughter of William Imison and Unknown, on 25 May 1857 in St John, Hoxton.
William next married Mary Ann Cornwall, daughter of Edward Cornwall and Catherine, on 7 Oct 1878 in St James the Great, Bethnal Green. (Mary Ann Cornwall was born on 3 May 1842 in Whitechapel, Middlesex, christened on 5 Oct 1842 in St Mary, Whitechapel and died Q1 1913 in Shoreditch, Middlesex.)