Another challenge I'm facing as I plot out my alternate history is just how much I can change such details of real people's lives as whom they married and when they died. This is a non-magical alternate history, so it's not like George III is going to be eaten by a dragon or Napoleon is going to be bewitched into marrying a sorceress. So I'm trying to work within natural causes--e.g. if I know a person had a severe illness or injury (or even fought in a battle or traveled to a place where he could've reasonably contracted malaria, cholera, or whatever) and survived, I can justify killing him off. Or, conversely, if someone died of something people had a reasonable chance of surviving, I can make him or her live. (For example, and this is NOT part of my story, what if Stonewall Jackson had survived the amputation of his arm after Chancellorsville? Lots of people survived amputations, or there wouldn't have been any point in subjecting anyone to them, and I bet the Civil War would've played out entirely differently had he lived, since with all due respect to Lee I think Jackson was the most gifted general the Confederacy had.)
Anyway. My specific plotting dilemma is whether I can marry real people to different people than they wed in real life, and, if so, whether I have to find another real person for them to marry, or if I can marry them off to a suitable invented person. In two cases, I think it's probable that my alternate reality would've led them to marry different people, and that marrying them off to their real-world spouses would be too contrived. But I can't see either of them staying single. So do I invent spouses for them? Or do I find other real people of roughly the right age and rank? Either feels a bit presumptuous, somehow. Though, really, I don't suppose it's any more so than killing people early or changing the outcome of battles. Maybe it's just because love and marriage are a bit more intimate than whether one survives an illness or whether the reinforcements make it to the battlefield on time.