I have found Scottish naming patterns to be a useful starting point in researching my ancestors in early North America - not proof, but a starting point for a line of inquiry in the absence of hard evidence. A kind of circumstantial evidence, it can help to create a working hypothesis, or support a conclusion in combination with a preponderance of other evidence.
It is more helpful further in the past, where evidence is scarcer and the naming pattern stronger. But even when my first son was born in 1978, my mother told me it was traditional to include a grandfather's name, even if only as a middle name. I did so. And I had never understood why my uncle was named Junior, when my father was the first-born son. When I learned about the Scottish naming pattern, it made sense.
There was some flexibility. You would only name a second son the same name as the first if the first one died. I have seen the same name recycled several times in this way in early New England. Few people nowadays would do that. We would probably think of it as morbid, or a jinx. So why did they do it? It must have been very important to them. They were like us - it was important to them to remember who their ancestors were, to pass that on to their children. The order of the names told them who their ancestors were.
But it's true that it can lead to confusion, even if the duplicate names are of cousins, not brothers. I have spent years trying to sort this out in several family lines in early New England, New York, and the mid-Atlantic states. I am not unique in this struggle. But even the duplicates are a clue - If you have a bunch of men with the same given and surname in the same area, migrating in the same patterns, it's likely they are related. Given names that have been handed down can be also a very helpful important clue for identifying women. Helpful - but not definitive. As I said, before, it is a starting place, a clue, circumstantial evidence.
I credit most of my understanding of naming patterns, or "onomastics" to John B Robb. Here is a link to his website:
His research was based more on quantitative analysis of naming patterns he found amongst the Scotch-Irish in early America. "The Chesapeake Tidewater Onomastic Pattern" [© John Barrett Robb; published 13Jan2015] gives a concise overview of the topic, distinguishing the naming patterns in the colonies around the Chesapeake Bay from the Scottish pattern, and gives a few references. In "TheScottishOnomasticPattern.pdf", [© John Barrett Robb; published 5Mar2012], he goes into detail about what he calls the the "Ancestral" and the "Parental" Scottish patterns. As far as their prevalance in different areas of Scotland, he says
"Several authorities I’ve consulted, including a Scottish-based professor of onomastics, have come up blank when asked about published scholarly studies on the history and application of this pattern in Scotland itself, and yet it seems to be almost universally known in that culture, as though by osmosis, if no longer extensively followed." [p. 1, footnote 1]
Like the naming patterns, these articles are a good starting point for learning more about this topic.