Hello Again
Lets see what we can find.
I doubt Martha Carter is his mother as she seems to have been burried ata Tarrant Gunville 20th July 1796.
The couple had three children Maria 1780 to her burial at Tarrant Gunville 19.5.1803 age 26.William 1789 married Ann Scholfield at the Savoy in 1813 and is a plumber in Hillingdon /Uxbridge area and your John who seems to have married Sarah Walding at Hanwell 7.10.1821.The witnesses Sophia Busby and Richard Mann don't help and I can't find the ful details of William's marriage.
But I did find a Poor law document for Thomas Kerly/Kearley on Ancestry for 1809.
He is a smith born in Blandford where intially he worked with hisfather and then brother Bonnet Kerley.He then moved to Gunville where he worked for John Moody for 5 shillings a week and married his late first wife Martha with whom he has 3 children Maria,William and John .A year past he married again his wife Ann.
This is a settlement statement for Bere Regis
We can see Thomas married Martha Moody 22.12.1777 at T Gunville
and Ann Davis at Bere Regis 29.12.1808 wit Thomas Horsey and William Rawles.
Children James 1.12.1809 at Bere privately ,James 10.11.1811 (became ag lab) and Bennett 10.11.1811-1.4.1812 at TG ,Eliza 16.10.1814 TG a blacksmith ,Bennett 21.6.1818 at TG.-2.11.1906 TG.a blacksmith.
In 1841 Ann age 55 y is living with her youngest son Bennett age 20 blacksmith at Tarrant Gunville next door to son James 30 ag lab wife Jane 30,son Francis 7 and daughter Ann 7 mths.
I see Thomas's death -9.6.1822 age 69 and apparently his gravestone has surviuved in the church yard at TG ,inscrption husband of Ann buried 13.12.1851 age 69.
So moving on to
Thomas's baptism at Blandford Forum 1.1.1753 son of John Kerley Siblings Mary Kerley 23.5.1735 (strangely a burial 23.4.1735) ,
Bennett Kerly 29.10.1737-9.8.1800 , Elis Carely 14.6.1738,Eliz Carely 10.10.1739-18.5.1740 ,Richard Kerly buried 9.11.1739 ,Richard Carely 2.4.1742 , Hubert Carely 25.7.1742-16.12.1776 ,Mary Carley 2.9.1745, John Carely 21.4.1747,William Kerly 8.8.1747 and Sarah Kerley 24.11.1749.
Obviously some of those clash but there are few details to help.
A John Kerly married Ann Haring at Blandford 14.7.1733.
Bennett /Bonnett must have inherited the Smithy as the oldest son.
Thomas Blandford had been taken on as an apprentice by John in 1741.He also hired a Lucy Oxford as a servant before 1766 according to another settlement cert.And Edward Witt blacksmith before 1749 again a settlement document.
Wife Ann died 19.11.1747 and was buried on the 21st.So he must have remarried,but there may be two of them .
John was burried 6.7.1769 no age given,or 3.2.1775 John Kerly senior .
Elizabeth wife of John Kerly burried 20.5.1773 and Elizabeth widdow of John Kerly senior 29.3.1790.
There is an Admin granted for John Kerly 1769 to his widow Mary .He is descibed as a blacksmith of Blandford Forum.Witness William Fry.It also mentions Bennett Kerley son.
The Inventry comes to £36 8 idOnly possible marriages I can see for a John and Mary is at Cranborne 28.11.1729 to a Mary Clarke,or farther out at Donhead St Andrew to a Mary Bennett of Berwick st John 10.4.1737 .
I'd go for the latter but it does mean you are left with which of the children at Blandford are from John and Mary and which John and Ann.
ps the famous Viscount Devonport is a relation.He is the son of George Ewbank Kearley 1814-76 who is son of William Kearley 1789 -28.7.1846 Hillingdon and Ann Schofield ,John's elder brother.
and sister in law.
There is a picture of Thomas's forge here.
https://historicengland.org.uk/images-books/photos/item/IOE01/00829/21And if I'd had to guess at a grandfather for Thomas I'd go for Richard Kerly the smith at Donhead St Mary.But I can't see the proof.
Ciderdrinker