In a letter dated Jan. 24, 1774, James Madison writes to William Bradford: "I am pleased that you are going to converse with the Edwards and Henrys and Charleses, &c., &c., who have swayed the British sceptre, though I believe you will find some of them dirty and unprofitable companions, unless you will glean instruction from their follies, and fall more in love with liberty by beholding such detestable pictures of tyranny and cruelty."
Who are the "Edwards and Henrys and Charleses" to whom he's referring?
Not a historian of the United States, but it seems pretty clear he's referring to British Monarchs. Edward, Henry, and Charles are all names of English (and later British) monarchs, and he refers to them as having "swayed the British sceptre". Sceptres are a pretty standard symbol for royals.
Further, this copy of the letter, found at the website of the National Archives and Record Administration, shows a footnote on that line referring to British monarchs.
EDIT: Looking a bit more closely at the fuller passage:
But away with Politicks! Let me address you as a Student and Philosopher & not as a Patriot now. I am pleased that you are going to converse with the Edwards and Henry’s & Charles &c &c who have swayed the British Sceptre though I believe you will find some of them dirty and unprofitable Companions unless you will glean Instruction from their follies and fall more in love with Liberty by beholding such detestable pictures of Tyranny and Cruelty.
Madison is referring to the study of history here, likely through reading some historical work. Hence the "convers[ing] with the Edwards and Henry’s & Charles &c &c"
I suppose it's possible he's referring to specific individuals but I think it's more likely just generic British names and he's inferring the British as a whole. Those 3 names are also 3 of the most popular British monarch names throughout history.