My Family Tree

Assuming for now that these Collins who came from Sligo, Ireland and married into the same Myers & Shafers family are related.
Thomas and William were neighbors in 1851 Williamsburg Twp, Dundas, Ontario, Canada. Both immigrated 1841/1842, and both were Church of England. It is very likely they were brothers, while John is less likely a brother.
http://ontariocensus.rootsweb.ancestry.com/transcripts/1851/477-4.html

Another Collins in the tree of "Helen Peck Huersch", who appears in photos with my grandmother, Lela Myers McRoberts, is "Robert Collins" b~1800. Lived in Lockridge, Jefferson, IA (between Bloomingdale & Des Moines, IA). Some of the same given names: Robert, William, Maria, Jane, Sarah. See in tree here - https://www.ancestry.com/family-tree/person/tree/104818087/person/410040066451/facts [After much research, appears Helen Huersch's husband worked with Jim McRoberts in the railroad office]

A single marriage online for a William & Margaret: William Collins and Margaret Leihy 12 Nov 1797, Cloyne, Cork, Ireland (Catholic). Witness: John Hogue & Garret O'Brien , by Rev. Jos Clancy.

The only source I have found for an origin in Sligo, Ireland is the late Janice Casselman who was told that by long time Collins researcher, the late Beatrice Collins, granddaughter of James Collins (b.1826 Sligo, Ireland). Credible family lore. How to reconcile with Eliza Collins "born in Dublin, Ireland 1823"?) Dublin may have been only the port of departure from Ireland. Daughter Agnes death cert has "County Demar, Ireland" which does not exist - could be Dromore or Doomore in Sligo. Beatrice’ father, Andrew Broder Collins, was named after the respected merchant and elected representative, Andrew Broder of Dundas. Andrew Broder’s father William came from Kilfree, Sligo, and was born in Ballymote, Sligo, which is adjacent (3 miles from) Doomore. It’s possible the families knew each other in Sligo, or at least knew each others hometowns.

John and Elizabeth Collins live in Osnabruck Twp, Stormont, Ontario, and came much earlier - before 1824 and practiced Universalism.
William and Thomas practiced "Ch of England"

Related?
5 August, 1796 • East half lot 36, second concession, "Osnaburgh" County of Stormont Eastern District. "With John Collins* Certificate". You will note although his certificate was written with the mis-spelling "Louks" the name on the description, was recorded as " Winiaffl Loucks ^ William Loucks, U. E. was living in Williamsburg Township, County of Dundas, in the year 1796, The "Osnaburgh" was taken off the Certificate.
https://archive.org/stream/hcblouckstr14/hcblouckstr14_djvu.txt

The 1749 Census of County Sligo, Diocese of Elphin, has a single Collins: "pg 410 Collins, Patrick" but he Catholic
Many more Cullen's tho:
386 Cullane, Thady
406 Cullane, William (single)
420 Cullen, John
445 Cullen, Sarah
391 Cullian, Edmond
425 Cullinen, Carnack
432 Killicollen, John

DNA match to Kilcullen's from Sligo. There were Kilcullen's in Dromore.

Curious Naturalization Record - https://www.familysearch.org/ark:/61903/3:1:3QSQ-G9SG-4949-K?i=230&cc=2040051&personaUrl=%2Fark%3A%2F61903%2F1%3A1%3A481H-W7ZM
Patrick Collins of Stafford, NH was born 15 Aug 1822 Sligo, Ireland and arrived in Boston 9 Jul 1842
No further record and no use of Patrick (a Catholic name) in our Collins.

Collins in Achonry: Patrick Igo married Anne Collins 7th? Jan 1835.
Thomas Collins b.1836 Claragh, Sligo, Ireland immigrates 1861 to NY, enters Alms House NY 1896. Claragh is 8 miles from Doomore.
John Collins b.1833 Achonry went to New South Wales, Austrailia
John Collins b.1833 Sligo married Sarah moved to Armagh, Ireland and is Church of England.
William Collins b.1835 Achrony (s/o Michael Collins and Catherin Davy?) went to Victoria, Australia
Sister of William, Mary b.1827 Tobercurry, Sligo. (Tobercurry in Achonry)
Thomas Collins of Achonry, Moylough, Sligo, Ireland 1827 Tax Assessment
Eneas Collins born in Achronry, Sligo 1808, living in Bellahy, Sligo 1856, d. Swineford, Mayo 1866 - all records are civil. Had daughters Margaret & Maria.
All of Sligo:
James Collins b.1821 Sligo went to Congleton, Cheshire, England.
Owen Collins b.1828 Sligo died 1878 in Cuyahoga, Ohio, naturalized there in 1871.
James Collins b.Jan 1831 Sligo arrived 1854 Boston
Miley Collins b.15 Dec 1835 Sligo, Ireland Arrival 12 Aug 1859 Boston
Ed Collin b.1 May 1841 County Sligo, Ireland Arrival 25 Nov 1857 New York

The Christy & Robinson families in Williamsburg came from Co. Armagh, Ireland.

Both A William Collins and a Thomas Collins are in early tax records of Crumlin, Dublin, Ireland, plus one William Collins there married and had children by Jane:
William Collins
Christening Date 18 Aug 1839
Christening Place Crumlin, County Dublin, Ireland
Father's Name William Collins
Mother's Name Jane
- and -
Ellenor Collins
Christening Date 18 Dec 1836
Christening Place Crumlin, County Dublin, Ireland
Father's Name William Collins
Mother's Name Jane

Possible theory to explain why they were protestant and I have no Irish DNA - they were immigrants from Wales or England, stationed there or given land in lieue of money for military service. So the Collins may have been in Ireland for generations.
Cooper's Lodge from "Hidden Histories: Political/Historical Perspectives of Sligo"

"Edward Cooper, who owned Markree Castle, had a shooting lodge in the mountain in the 1600s above Dromore West. He was a cornet, the lowest rung of commissioned cavalry officers in the British army. When the Cromwellian wars ended and the Crown restored, there was no money to pay the soldiers who fought. The soldiers were given small holdings of land in Ireland as payment instead of cash. Cooper was in Coote’s regiment (Welsh) and most of the soldiers received land in this area. The soldiers were not anxious to come to Ireland at the time. Cooper then bought their shares of land cheaply and made an estate, first in Limerick, and then bought plots in Sligo from the soldiers he knew in Coote’s regiment.

There were big parties in Cooper’s Lodge, especially during shooting season, for all of Cooper’s visiting friends. The last caretaker in Cooper’s Lodge was murdered more than 100 years ago. He was beaten up and left in the street, so a policeman came along and investigated. The man lay dying and the policeman leaned down and put his ear to the man’s face. The man said something to the policeman and then passed away. It was never known what the policeman was told. The lodge is in ruins now."