Hi Jo,
Have you seen this family tree on ant*sy?
Source citations are ants*y.com.au. It may be worth tracking down.
William Pitt b. 1799 Wiltshire County, England, United Kingdom
Jane B. Giles b.1801 Gloucestershire, England, United Kingdom (spouse, no marriage date)
Children:
William Pitt b. 1820 Sunderland, Durham, England. d. 1879
Thomas Pitt b. 1826
1830 Second Marriage to Grace Amelia Seymor b. Kingston House, Dorset, England
Children: Ann Pitt b. 1831
For William Pitt (Jr.) b.September 18, 1820:
Marriage to Jane Dixon in 1850 in Sunderland, Durham England
d. 1879 Melbourne, Australia
Children:
William Pitt (Architect) 1855-1918
Alice Pitt 1857-1879
Richard Brinsley Pitt 1860-1929
Charles Pavey Pitt 1865-1944
Deb