Settle a spousal argument...
Isn't arguing with your spouse just the best part of renovating??
We are currently replacing a window in our house. The one we took out was already not an original; the house has in fact all aluminum windows from the '70s or so. We replaced it with one the same size - about 5 feet wide and 6 feet high (the new one is divided into sections; the old one was mostly a single fixed pane). We think the aluminum unit likely replaced a pair of double-hung windows - in fact, one of the weights and a pulley wheel were still in the cavity. And in addition as we took things apart we found the usual horror show of bits of wood, hacked off headers, mortar filling in the central post gap, and the like.
ANYWAY, once we had the window in, we noticed that opening and closing it generated a bit of movement in the whole wall, suggesting it is not the most stable thing on the planet, and got to discussing what the original structure would have been. One of us thinks that the original two windows would have had a continuous stud running up between them (thus using two shorter headers and each window disrupting only one stud), while the other thinks that even that original pair of windows would have been a single unit with a single header spanning the entire 5 foot distance (cutting 3 studs). That there is a single, likely original, sill complicates things.
As we have no original sets of windows left in our house, we can't settle this. Perhaps someone else can?