Revisiting Old Data
I came across this information in an old posting of mine to andrew-buchanan@yahoogroups.com
Date:  24 Feb 2006, 04:07:31 PM
Subject:  Early History of Elma Township [Perth County, Ontario, Canada - where my Buchanans settled in the autumn of 1847.
["The Elmanac" is a history of Elma Township]

I would like to call your attention to to the phrase "The names in this group include Joseph Caruth, James and Robert Buchanan, John Porter, David Glen, and Robert Thompson."

If two brothers of Ann Thompson Buchanan came to Canada with the family, William and Robert Thompson seem like the most probable candidates. [This was even prior to being aware of her father James Thompson's probate in Australia.]

The earliest (1861) census lists these Thompsons:
Thompson Henry (b. 1822 Ontario),
Thompson John (b. 1810 Ireland, child b. 1842 Ontario),
Thompston Robert (b. 1820 Ireland, child b. 1843 Ontario)
Thompson William (b. 1816 Ireland, child b. 1845 Ontario),
Thompston William (b. 1820 Ireland, child b. 1843 Ontario),
Thompson William (b. 1822 Ireland, child b. 1847, Ontario).
So of this group only the last William Thompson seems like a possible candidate, if the ages and birthplaces are accurate. [Since the others apparently arrived before 1847]

Thompson William L 33 C 12 Farmer Ireland Ang 38 Married Male  1822
Thompson Jane   " " 30 Married Female  1830 [This might be Jane Love, who married a William Thompson on 27 Jan 1847 in Urney Presbyterian Church, Urney Parish, Tyrone, Ireland]
Thompson Margaret   Ontario " 13 S F  1847
Thompson James   " " 11 S M  1849
Thompson Ann   " " 9 S F  1851
Thompson Jane   " " 7 S F  1853
Thompson John   " " 5 S M  1855
Thompson Joseph   " " 3 S M  1857
Thompson ?   " " ? S M
[The last number is a calculated year of birth, which I have added.]

Other accounts have a William Thompson leading the first group of settlers
to Elma, but which one of the three?

I wondered if John Porter was one of our group, since Charles Buchanan was
married to Ann Porter.

From the 1861 census, it looks possible.
Porter John L 35 C 11 Farmer Ireland Meth 32 Married Male  1828
Porter Ann   " " 31 Married Female  1829
Porter Robert   Ontario " 13 S M  1847
Porter Thomas   " " 11 S M  1849
Porter John   " " 9 S M  1851
Porter William   " " 7 S M  1853
Porter Mary Ann   " " 5 S F  1855
Porter Jacob   " " 3 S M  1857
Porter M. Jane   " " 1 S F  1859

I wondered if David Glenn might be related to Elizabeth Glenn, who married James Buchanan.
I see the same pattern of immigration here. [i.e. born in Ireland in 1810-1820 and has children born in Ontario in the late 1840s] But Elizabeth is too old to be the daughter of David's wife Mary. Maybe David is her brother or cousin.
Glenn David L 35 C 11 Farmer Ireland Pres 45 Married Male  1815
Glenn Mary   " " 33 Married Female  1827
Glenn M. Jane   Ontario " 13 S F  1847
Glenn Margaret   " " 11 S F  1849
Glenn James   " " 9 S M  1851
Glenn Matilda   " " 7 S F  1853
Glenn William   " " 5 S M  1855
Glenn Sarah   " " 1 S F  1859

Buchanan James L 25 C 12 Farmer Ireland Meth 36 Married Male  1824
Buchanan Elizabeth   " " 22 Married Female  1838
Glenn Catherine  Servant Ontario " 15 S F  1845
Buchanan M. J.   " " 2 S F  1858
Buchanan Andrew   " " 1 S M  1859

There is also an Alexander Glen aged 40 and a Charles Glenn aged 27 in the 1851 census of Mornington, but no Elizabeth or Catherine. Elizabeth might belong to one of these families.

Bill
[The Elmanac, the History of Elma Township 1857 - 1997, pp. 4-5]