He was probably the son of George and Elizabeth Watson of Clonsast. Clonsast records do exist, but do not actually give any information other than the birth. A William Watson of Clonsast was born there on 28 October 1818 (John Watson was also born in Clonsast on 15 Oct 1820 and Henry Watson on 29 September 1822. I would assume that they were brothers). This would have put William Watson at 24 when he married in Sep1843, but also means he was 73 when he died and not 62 as on his death certificate - his headstone in fact does say he died aged 72.
William Watson is cited as a farmer and later as a grocer and fishmonger. He married Elizabeth Blong in Lea Parish church 18 Sept 1843 according to the register of Lea Church (The date is correct, it is to the right woman, and fits the births of their children). They married by licence and the witnesses were William Bradley and George Watson. He is given as from Clonsast when he married in Lea Church Portarlington. Their first children were born at Clonsast (the parish records give 3 children born in Clonsast) and then to Harristown, Kildare, where 2 further children were born between 1853 and 1860. The last child, Susan, was born about 1862, and I have not ascertain where this was. I suspect it was at Portarlington, Portarlington records exist, as it is not in Monasterevin, and they had moved back to Portarlington before Marie's marriage in 1880 to Thomas Grant. Their children from church records are
Harristown is in Parish of Monasterevin, which in addition to the district of Monasterevin proper, the present parish includes the old parochial districts of Kildangan, Nurney, Duneany, Harristown, Walterstown, Ballybracken, Lackagh, and part of Lea, all which,-except the townland of Inchacooly, in the Queen’s County,-are in the county of Kildare.
1853 Griffiths gives William Watson of Clonshannon, Clonsast, Offaly and there is no William Watson listed in Harristown, Kildare in 1853 Griffiths (his landlord is given as Thomas Watson and there are 6 other Watsons living in Clonsast Parish at that time). Coupled with the fact that the first mention of them in Harristown is the birth of a child in August 1853, this perhaps indicates that William Watson moved to Kildare in the spring or summer of 1853. The only other "William Watsons" recorded in Griffiths are:- for Kidare none, Offaly has one at Castlejordan and one at Ballynakill, Laois has one at Offerlane.
A tentitive interpretation of the Griffiths Watsons in Clonsast would be that father George Watson and his 3 sons William, Henry and John all have land there. That leaves Thomas, who holds a lot of land and Benjamin who are not the immediate family of William Watson, but probably related.
Description in Parliamentary Gazeteer 1846
1874 William Watson of Portarlington was granted transfer of Liquor Licence from George Blong on 2 Jan 1874. George Blong, his father in law had died the previous month.
Died 17 July 1892 age 73 (his gravestone says aged 72, and the age on his death cert has to be wrong as he was married in 1843. A farmer of Portarlington. Death reported by Susan Connolly (his wife Elizabeth Blong's sister, Susan Blong who has married Henry Connolly). This is certainly the right man, but if his age is correct then he would only have been 13 when he married in 1843. My conclusion is that he was born in 1818 as recorded in Clonsast parish and that the age on his death certificate is wrong.
On the above chart the Clonsast records shows on 4 Feb 1841 that John Smallhorn of Lea Parish marries Margaret Watson of Clonsast "with parents consent" which implies that one or both were under 21 years old.
Watson Church Records from Portarlington
Watson Clonsast records
I met Olive Chadwick (nee Watson) in Feb 2009 at her house in Clonsast (086 1051934), but she was not able to add to the picture. She suggested contacting Bobbie Ward 057 8629075 whose grandfather was a Robert Watson