Naturally the mother-in-law walking in and out cramped a chap's style, [...]"
When my parents married in 1938 they lived with the maternal parents for a while. My father and mother were forbidden to be upstairs together during the day time.
Contrast that with the generation born since about 1990 - where kids bring their current love interest home for the night with their parents' acceptance. Not that the latter always approve of the current chosen one.