The similarities and continuities between the English Civil War (1642-51), the second British Civil War, alias the American Revolution (1775-1783), and the Second American Revolution alias the War Between States or the American Civil War (1861-1865) have attracted much comment. (If the British Government before 1775 had had the resources of Geni to track the ominous rise of "Oliver" as a first name in the northern American colonies, it might have realised that there was dangerous ground here).
What has struck me by doing the English Civil War is how common it was for father and son, or brother and brother, to take opposing sides. The well-known example of the Verneys (where the father who sadly took the Royalist side, but ordered his steward to give the best pistol in the house to his son on the Parliamentary side) was not at all uncommon. This may have been tragic, temporarily but must have aided reconciliation after the Restoration. I think I can see something of the same pattern in the American Revolutionary War (the Coffins, for example, or the series of British Generals and Admirals who were married to Americans or who had American mothers). But reconciliation was more difficult because there was no Restoration, so most Tories who sided with the British simply had to leave.
In the third Civil War there must have been some cases where families were divided, in the border states (West Virginia, for example, or Eastern Tennessee), But simple geography meant that most families were undivided in their affiliations. Fine for the victors; but a sullen South caused problems for 100 years.
Mark