A friend recently forwarded Céad Míle Fáilte – and welcome to your "Letter from Ireland". We're A Letter from Ireland with a story about one of the first Irish immigrants to Canada, possibly the first. The weekly Letter from Ireland is produced by husband and wife team Mike and Carina, who live in County Cork, Ireland.

The letter that my friend shared was about Tadhg Cornelius O'Brennan, who appeared in the first census of Ville Marie (today known as Montreal) in 1663. The letter asks what would bring Tadhg to the new world, 200 years before many of his Irish Catholic neighbours. The answer may lie in the actions of Oliver Cromwell, the English statesman, politician and soldier who led the reconquest of Ireland by the forces of the English Parliament. In 1652, the Parliament of the Commonwealth of England, Scotland and Ireland passed an Act of Settlement, "confiscating the majority of Catholic-owned land and granting it to English and Scottish settlers." The letter states: "Among the land affected was that belonging to the O’Brennans for hundreds of years previously."

Like some others in Ireland, says the letter, Tadhg chose to join the Army of France. He moved to the Celtic region of Brittany in Northern France, one of the regions that supplied soldiers to New France.

The first record of Tadhg in New France—according to the Letter from Ireland—appeared in 1661, when he was noted as working for a local farmer: "we hear of him only because he was one of a number kidnapped by a band of Iroquois," says the letter. A captive between March and October 1661, Tadhg managed to escape. By 1663, he appeared in the census of Ville Marie, now known as "Thecle Cornelius Aubrenan."

The extreme imbalance between men and women in the colony—for example, the 1663 Ville Marie census recorded 1,293 single men but only 9 women of childbearing age, says the letter—led King Louis XIV of France to send the Filles du Roi (the King's Daughters) to help close the gender gap. Between 1663 and 1673, more than 700 Filles du Roi—women who were offered allowances to cover the cost of clothing and passage to the new world as well as dowries when they married—came to New France.

Try as he might to secure a wife in Ville Marie, Tadhg was unsuccessful. By 1670, he headed upriver to Quebec City, where he met Jeanne Chartier, a Fille du Roi. They were married on September 10, 1670, in Notre-Dame-de-Québec, the first Catholic church in New France. In their marriage record in Généalogie Québec, Tadhg is known as Thecle Aubrenam, originally from Ireland; Jeanne Chartier is noted as being from France. In his connected individual Généalogie Québec record, Tadhg is referred to as Thecle Aubry Cornelius. Thecle and Jeanne would have seven children.

A more detailed account of the lives of Thècle Cornelius Aubry and Jeanne Chartier appears in the excellent bilingual website The French Canadian Genealogist. Created by Ottawa-born Kim Kujawski—"a bilingual genealogist with a passion for uncovering family histories"—this site also provides an excellent entry on the Filles du Roi.

In sending me the Letter from Ireland, my friend asked whether there were ancestors with the name Aubry on my mom's side of the family. I hadn't recalled coming across the name Aubry in my previous searches but, of course, my quests to that point had focused on the male lines, the carriers of such names as Pagé and Charbonneau.

The only way I knew to try to determine whether there was a connection between Tadgh and my mom was to start with Tadgh's entry in Généalogie Québec and to read through the long list of his descendants. This proved to be a painstaking process. It was like looking for a needle in a haystack, with no guarantee that such a needle even existed. Working my way through the tree, I clicked on every plus symbol to expand groups of descendants. I scanned the names, looking for ones that I recognized: Charbonneau, Tessier, Campeau, Pagé.

Hours into the slow crawl through the names of thousands of descendants, I expanded a group and saw something that I hadn't seen before: a greyed-out name. That suggested that I had visited that person's record before. The name was Marguerite Chenet. I clicked on the link and landed on the page of my great-great-grandmother.

From there, it was relatively easy work to retrace my steps back to Tadhg, or Thecle as he was known in the records. Here is the path from an Irish immigrant and a French Fille du Roi to me:

And that leads to me.

My curiosity was rewarded with a family connection to a fascinating story—my favourite type of genealogical find.