Who should share rooms?

[CuriousInIL]

In a response yesterday, it was stated:

Unless the room is a suite (in which sleeping areas in separate rooms can be arranged), it is not a good idea for a grown woman to share a hotel room with a grown man, unless he is her husband. I recommend getting two rooms; one of them to be shared by you and your friend, and the other to be used by her father.

Given that it only says husband and that the suggestion was for the women to be separated from the man, was this intended to indicate that “it is not a good idea” for a 20-year-old (which I do not consider grown) or even a grown woman to share a hotel room with her father?

 

[Michelle_Arnold]

It’s a matter of personal opinion and prudence, of course, which is why I qualified my statement with “it is not a good idea” (as distinguished from “it is morally unacceptable”), but I do indeed think that, at least in Western society, a grown child ordinarily should not share a single bedroom with a parent of the opposite sex.

We also disagree on whether or not a 20-year-old is an adult. A 20-year-old in the United States is considered to be a legal adult (excepting only those privileges that require an age of 21 or older). Certainly it would have been unheard-of only fifty years ago for someone of that age not to be considered fully grown.