In 1836 Mitchell was born in Sydney, the son of Dr James Mitchell and his wife Augusta Maria Frederick,
née Scott. James and Augusta are commemorated by a window in the
Garrison Church. David Mitchell was born at Sydney Hospital, Mitchell won scholarships in mathematics and graduated B.A. in 1856 with honours in classics, and M.A. in 1859. It was said that he declined the position of attorney-general. Mitchell assisted in the management of the Hunter River estates. Allegedly, he broke off a romance with
Emily Matilda Manning, daughter of
William Montagu Manning. Mitchell's father died in 1869. Publication of the family affairs was humiliating to a man of Mitchell's sensitive disposition. ==Book collector==