The title of this post may conjure up memories of a college roommate you have not seen in years.

It’s about those relationships given in documents or records that can be interpreted in one of many ways. Sister-in-law or brother-in-law are two of those relationships. I have a sister-in-law who is my brother’s wife and another sister-in-law who is my wife’s sister. Had my wife’s brother married, his wife would also have been my sister-in-law. Keep in mind that for some relationships, “in-law” or “step” may never be used when describing the relationship. Individuals may be referred to as “nephews” whether they are biological or related by marriage.

And of course the difference matters to a genealogist and when analyzing DNA matches or those individuals who “fail to match.”

When the phrase used to describe the relationship is vague, consider all the possibilities.