What's a "collateral line"? Most genealogy researchers focus on their direct blook line. A collateral line is a different branch; your cousins are collateral from your direct line. The key part is that your line and your cousin's line will eventually meet, making your research and hers the same. Okay, so your cousin is a bad example since you probably know each other already. But what happens back 3 or 4 generations? Can researching your great-grandfather's brothers and sisters help you?

The short answer is: maybe. It depends upon what you find. So you want an example? Okay, here goes.

The background

There's a family story about my great-grandfather Jeremiah Shay that says he emigrated from Ireland when he was about 11. His death certificate says he was born July 13, 1857 in Ireland. So 11 years later puts us in 1868 (or so). Off to the passenger lists. Nothing. Plus or minus 2 years. Nothing.

Back to the story: His mother wrapped her shawl around him for a coat. Nice image but no help there. Young Jerry traveled with a brother but no one remembers the brother's name. But he didn't travel alone. Back to the passenger lists. Nothing.

Several years pass while revisiting the passenger lists now and then, but not worrying that bone too much. I mean, there are other ancestors to be found.

Revisit what you do know or think you know

Then a cousin showed me great-grandpa's diary from 1914. Remember that personal effect, photographs, and other things get distributed to different descendants. Remember those collaterals? So I read through the diary day-by-day. Most of the entries are about things he did and wanted to remember. Short notes. Confusing ones (to me), like "ditching with Dutcher". Pretty sure Dutcher was a person. And I scanned every page of the diary (thank you technology). And I found several gems.

• January 6: Jennie [his daughter] got married to Raymond Wall at Scranton.
• March 22: Went to Mass with Patsy [his son Patrick who must have been visiting].
• March 29: Went to Mass high water in river over flats 21 feet flood.
• April 15: Fished with PM.
• May 27: Went to Laquin on 2. Came to Towanda on 5. John McNiff killed at Elmira this PM by falling from train when returning from his work.
• May 29: Mrs. Shay myself and Elizabeth went to Horseheads to attend Burial of John McNiff.
• May 30: At funeral at Horseheads. Came home on LV work train. [LV = Lehigh Valley Railroad]
• June 14: Went to Mass. R. Wall [his son-in-law] at Towanda …

And it goes on. A couple years after I first read the diary the John McNiff entries on May 27, 29, and 30 'suddenly' stood out. Why would this man that spent so much of his time keeping trains running between Towanda and Williamsport stop for a funeral. He worked Sundays if necessary and he seemed to fit his family and fishing or hunting between the back and forth.

So I started trying to figure out why a man that lived 40 miles to the north – when Jerry's trains traveled in the opposite direction – was important enough to stop and attend a funeral. Jerry's wife and one daughter went along. And they stayed over night. So we're talking a day, a night, and part of another day. The trip by train from Towanda to Elmira did not take that long since the LV had a station in Towanda too, but, … he took off from work.

Follow a collateral line

I found the answer almost immediately starting in the 1910 census on ancestry.com. John McNiff was Jeremiah Shay's brother-in-law. John's mother-in-law, Elenor Shay, was living with John & Mary NcNiff. So John & Mary McNiff are a collateral line. New people to learn about and, maybe, new researchers looking for your common ancestors.

Backtracking John & Mary in the census I found them in Horseheads in 1900. With her mother, my great-great grandmother. Going back again to 1880 I had to change towns to find the Shays living in or near the village of Millport. But Jeremiah was living nearby with his new in-laws (in 1880). John was living in Horseheads with his first wife, Maggie _____, and son Simeon. So Mary was his second wife. So many new stories to learn about, and people to remember … and memorialize.

Conclusion

So by researching some random name in a diary – one that stood out because his death made a hard-working man stop to pay respects in person – I found a marriage connection to my direct line. I found a new collateral line to research. I learned Jeremiah had a sister, Mary, which I didn't know before, and by researching her I found my great-great grandparents had emigrated also. Jerry Shay might have emigrated before them or they might have arrived together (I don't know yet) but I found new information about my own direct blood line by researching someone else.

Collaterals, therefore, might be important. You just don't know until you spend the time investigating. I've followed some collateral lines that went nowhere and others, like this one, that proved to be a gold mine.