Thanks for your message.
The beneficiary of Benjamin's will proved 20 Jan 1785 was John Davenport (b. 1755) who was the father of your John (b. 16 Dec 1787) and my ancestor Henry (b. 27 Oct 1789, chr. 22 Nov 1789). Neither John jr nor Henry were born when Benjamin died.
I have a family tree on Rootsweb called - Descendants of John Davenport (c1755-1804). John Davenport and Elizabeth Waterhouse and their 11 children were professionally researched in Lancashire by an agent, using all available records, and further research has been done in the archives by family members, so I am pretty confident that it is accurate.
At this point I believe that Elizabeth's parents were David Waterhouse and Elizabeth Greenwood, who married on 16 Nov 1745 in Yorkshire. But as I have not personally researched this I am happy for it to be proved different as I need the family tree to be accurate.
Your John Davenport (b.1787) married Alice Turner in St Wilfird's Church, Standish. A witness was his brother Waterhouse Davenport.
Marriage: 3 Nov 1823 St Wilfrids, Standish, Lancashire
John Davenport - of This Parish
Alice Turner - (X), of This Parish
Witness: Daniel Mellor; Waterhouse Davenport
Married by Banns by: George Whitlock, Asst. Curate
Marriages 1813 - 1825, Page 171, Entry 513; LDS Film 1526141
John's occupation was Calico Printer. Besides being a witness at family weddings, he was a witness at other marriages at St Wilfrid's Church, Standish, including: James Turner 31/12/1811, Edward Hindle 23/06/1816 [brother-in-law of his brother, David], Daniel Mellor 20/05/1816 and William Mellor 26/11/1821.
John and Alice had 9 children, 1 before marriage and 8 after).
1841 Census: Scholes Bank, Horwich:
John Davenport 50 Printer Y; Alice Davenport 40 Y; Waterhouse Davenport 15 Printer Y; Betty Davenport 10 Y; John Davenport 10 Y; Alice Davenport 7 Y; Mary Davenport 5 Y; Thomas Davenport 3.
Inscription from a Davenport headstone at Lee Lane Chapel, Horwich
In memory of WILLIAM son of JOHN and ALICE DAVENPORT born Aug 4th 1841 died Nov 6th 1845. Also of JOHN DAVENPORT who departed this life Oct 27th 1855 aged 68 years. Also the above ALICE DAVENPORT who departed this life Dec 1st 1883 aged 83 years. Also BENJAMIN son of the above JOHN and ALICE DAVENPORT who died Oct 7th 1893 aged 49 years.
Henry Davenport (b.1789) married Ellen German on 14 Sep 1812 in St Wilfrid's, Standish. A witness was his brother John. They had 10 children (1 before marriage and 9 after), including my great great grandfather, David Davenport (b.1814).
Marriage: 14 Sep 1812 St Wilfrids, Standish, Lancashire
Henry Davenport - of This Parish
Ellen German - (X), of The said Parish
Witness: John Davenport; William Darbyshire
Married by Banns by: John Airey, Asst. Curate
Marriages 1792 - 1812, Page 246, Entry 737; LDS Film 1526141