Eeeh, I'll put this here for now, might move it to the Jessamine Kaldwin page if I can't get an answer here.
Maybe someone can help me with this, because I'm highly curious.
I remember seeing a book during one of my playthroughs that talked about the Kaldwin line. I can't remember very much of it, but I specifically recall it talking about how the Kaldwin line is not the direct royal line--they came into power because a ruler some generations back lacked an heir, and the Kaldwins were his closest relatives.
I have not been able to find this book on my current playthrough (which is fine, since I'm only on The Royal Physician), and can't for the life of me remember where I found it the first time. Does anyone recall where this book might be?
Also, I have heard that the only Kaldwins which have been rulers of the Empire are Emily, Jessamine, and Jessamine's father, which would mean her father was the Euhorn Kaldwin who had Kaldwin's Bridge constructed. However, when Corvo is in the library at the Office of the High Overseer, the Overseer pouring over The Movements of Corvo Attano says to himself, "This map is old, older than the Kaldwins." Obviously he could mean the Kaldwins as in the aristocratic family, but I am curious now. Do we actually know how many emperors/empresses have come from the Kaldwin line?