Looking for information on my gggrandfather, particularly his birthplace in Ireland and whether there are any living descendents.

Thomas McDowell, Palmerston, Wallace township, Perth/Wellington Counties, Ontario, b. approx. 1827 or 1828 in Ireland, d. after 1907.

m. Sarah Thompson, b. approx. 1826 or 1827 in Ireland, d. betw. 1870 and 1907.
They had 4 sons and 6 daughters:

Isabella H. McDowell, b. 1853, m. 1878 to R.H. Robinson in Palmerston
William James McDowell (my ggrandfather, a miller and tinsmith) b.1855 in Palmerston.; d. betw. 1882-1891 (possibly in Hudson, Wisc.), m. in 1879 in Kincardine to Elizabeth Adams, b. 1859 in Fergus, Wellington Co., ONT; d. 1936, Baltimore, Md.; daughter of John Adams, a German-born shoemaker, and Margaret Adams of Kincardine, formerly of Fergus)
Mary Ann McDowell, b. 1857, m. 1878 to Wm. Christopher Frost (she was still living in Palmerston in 1907, had one daughter, Mary Ann)
Sarah Jane McDowell, b. 1858, m. 1878 to Alex Henry Hairell
Samuel J. McDowell, b. 1860, d. 1873 (I have a grisly record noting he died in a stave factory accident at age 10 in March 1873, getting caught on a belt)
Charles John McDowell, b. 1862
George A. McDowell, b. 1864
Allice McDowell, b. 1866
Ruth McDowell, b. 1868
Eliza (Lizie) McDowell, b. 1870

In 1994, a genealogist searched probate records for Perth and Wellington Counties and found nothing for Thomas McDowell. A history of Perth County suggest early settlers of Wallace Township were Ulster Irish. He settled alongside/about same time as William Thompson, John Kearns, Adam Ranton, and William Dalley. In Vera Ernst McNichols' 1966 "Reveries of a Pioneer," she writes in verse:
Lots 16,17, and 18 near Palmerston,
Were taken up in July 1854,
By Tom McDowell, quickly followed,
By Adam Ranton and four more,
Who had come up from Simcoe County,
Samuel Wilson and Simon Kearns,
Already experienced in bushland,
The Thompsons and Matthew Burns.

I'd be interested if any of their relatives know their Irish origins, since they may all have immigrated together. Are there any Thompson descendents still living in Palmerston (he married Sarah Thompson)?

He was the first Mayor of Palmerston, and lands owned by him (con. 11/lot 18) and neighbor William Thompson, became the railroad station and yards for the Wellington, Grey, and Bruce Railroad. There is an historical marker about him in the town park next to the old railway station.

I visited Palmerston in 1994, and while the local cemetery had a plot that he purchased, there is no record of him being buried there. The local newspaper building burned in the 1930s, so there are no newspaper records from Palmerston with his obituary. I did find a 1975 centennial newspaper edition with a reprinted story from 1907 which notes he was 14 when he arrived in Canada from Ireland, settling first in Tecumseh, Simcoe County, with his parents, and then moving to Palmerston. It notes he was approaching 80, with a very clear mind, living with his daughter, Mrs. W. C. Frost (Mary Ann). I have subsequently learned the Frost's had one daughter, Mary Ann, in the 1901 census.
Despite the 1907 newspaper article, the 1901 Census has no record of him.

Any help would be appreciated.