Gillian, The board would not allow me to link to the Postlethwaite page on my website. Here's the earliest I have:

Although there is no record, I believe John Postlethwaite (1761 - 1830) was son of WILLIAM POSTLETHWAITE & BRIDGETT BENSON and brother of WILLIAM POSTLETHWAITE Ch: 23 DEC 1759 St Mathews, Doug

JNO POSTLETHWAITE (1761 - 1830) m. MARTHA SAWREY (abt.1768-1803 dsg)

Jno Postlethwaite marriage: 28 DEC 1793 in Braddan, Isle of Man. (2nd of 3 wives**)
......i. Miles-1 Postlethwaite (1794-1832)(In Jno's will 1831)---------------->>>GEN 3
......ii.Williamson Postlethwaite (1795-?) probably in 1861 Census, called "William." (NIB)
......iii.Richard Williamson Postlethwaite (1797-1871 Goderich, ON, Canada) (NIB) -----> Using the name White, he married Jane Patterson (1796-?) in Quebec in 1823. 5 children, with surnames Brown, Gilders, Postlethwaite, & More.
......iv.Fletcher Postlethwaite (1799-?) (NIB)
......v.Alice Postlethwaite (1800-?) (NIB with Post name)(We know from Jno's will that she married John Brew)
......vi.Elizabeth Postlethwaite (1802-?) (NIB) (We know from Jno's will that she was not married in 1831)
......vii.Martha-2 Postlethwaite (1803-1803).
**Note: John's first, January 1791, marriage was to Hannah Lewthwaite who died in childbirth a year later. After Martha Sawry died in 1803, during the birth of their seventh child, John married Ann Keegan in 1816. She was the proprietress of the Brown Bobby in 1837 version of Pigot's Directory. 1817 was the first mention of the Brown Bobby, the infamous Public House run by this John Postlethwaite.