William Mitchell, the twin son of Jane Fitzgerald and William Mitchell was born on 9 October 1788 and baptised at St Philip's Church, Sydney on 26 October. He accompanied his mother to Norfolk Island on the Sirius in March 1790 and then returned to Sydney in 1793 on the Kitty in March 1793 with his father a former marine and soldier in the New South Wales Corps.
Mitchell joined the NSW Corps as a drummer in 25 July 1800. He was described as being 5 feet tall, with a thin sallow face, grey eyes, and light brown hair. He returned with his father to England in 1810.
'Mitchell, William (1788–?)', People Australia, National Centre of Biography, Australian National University, https://peopleaustralia.anu.edu.au/biography/mitchell-william-31022/text38392, accessed 2 June 2023.