Changing definitions can make it hard to keep track of just who is related to whom.

So often in genealogy, as with other disciplines, things are not quite as they appear. Genealogy is full of words that have shifted meaning over time— in ways that can lead to confusion.

I recall the first time I was disabused of the idea that only the children of my siblings or those of my wife were my nieces and nephews. I came across a will and found that the nephew was the testator’s grandson. In another time, the term nephew was a euphemism for a child born out of wedlock.

Then there was the case of John Murphy, Sr. and John Murphy, Jr. The trouble was that they weren’t father and son, not even uncle and nephew—they were not related at all, apparently. But in the rural district where both lived, people distinguished the one who was 10 years older by referring to him as John senior, the younger as John junior.

I was concerned about the criminal background of Mary Jones, in that she had an alias—Harris—until further research showed that Mrs. Jones had been previously married to the late Mr. Harris, and the first document failed to clarify the situation. Sometimes, instead of “alias,” a document will read “otherwise,” or even “orse” for short.

Then there are the inmates: people who lived in residences where they were tenants or lodgers, but not owners. The owner was the housekeeper, whether male or female. So if your ancestor was an inmate, you needn’t get the local crime sheet to see what he was in for; nor was he an orphan, indigent or ill. He simply lived there.

More recently, some women have chosen to use the prefix Ms. rather than Miss or Mrs. While people today pronounce Mrs. as “Missus,” even that form is relatively new. Before 1800, a married woman was called Mistress. With a capital letter, that meant living with one’s husband, but if she were referred to as a mistress, well, there was an understood but unstated implication.

Then there are those time-honoured trouble-making terms: step-brother and half brother. Long before the phrase “blended families” became commonplace, they existed, largely because people who had been widowed at an early age, or who were left with small children, remarried relatively quickly for practical, if not romantic, reasons. (After all, a man with four small kids couldn’t stay home with them if he had to fish or farm. No more could a woman with children support herself, given the narrow range of respectable occupations available for a woman at the time.)

When a woman with two boys married again and had a third child, that child had two half brothers, because they shared half the same parentage. If the man she married brought with him a daughter by a previous marriage, that girl was a half sister to the new baby. However, the girl was a step-sister to her stepmother’s two sons.

People often get those terms mixed up, I’ve found. You could not marry your half sibling, but you might be able to wed your step-sibling.

There was an unusual example of this in Halifax 200 years ago. A young couple wed. Several years later, the groom’s father, a widower, married the bride’s mother, a widow. The young couple became step-brother and step-sister. The son of that young couple then became half brother to a child born to the older couple.

I don’t think anyone ended up being his own grandpa, but they were flirting with the possibility.

Dr. Terrence M. Punch is the author of the forthcoming volume two of Some Early Scots in Maritime Canada. He was invested as a member of the Order of Canada this past September.