In s7e1 (set around 1941), Mary Ellen and Erin sharing a tiny loft room and a foldayway bed at a guesthouse. Erin likes this room, but Mary Ellen doesn’t.
I prefer posting brothers bedrooms, but there are very few foldaway beds.
The Waltons also have some other and better scenes at their home, mainly 3 brothers in one room and 3 sisters (rating 8). Also some guest and other constellations.