This question is awkward to ask, but it's still legitimate and has gone unanswered, as far as I can tell.
In shows like TNG, where ships carry officers and families, we know that there are Starfleet officers who are in romantic relationships. We know that officers are engaged sexually as well because Captain Jean-Luc Picard and Doctor Beverly Crusher
Have a kid, who appears in Star Trek: Picard as a fully grown Jack Crusher.
[Star Trek: Picard spoiler]
And, of course, we know at least two swashbuckling captains (Pike and Kirk) who are prone to sleeping around with various women in their brief, exploratory, interstellar relationships. This is despite the fact that Starfleet has some rules against these kinds of relationships, although they're absolutely pointless since nobody pays them any heed whatsoever.
My question is, how do lower-ranking officers (e.g. such as ensigns and lieutenants) copulate? They lack the privacy that captains and commanders are afforded thanks to their large, private quarters. I could make an example of how "Lower Deckers" in Star Trek: Lower Decks literally sleep in the walls of the corridors, but this sleeping arrangement is most likely comical exaggeration, or specific to the California class. I also remember one scene (perhaps from a Star Trek: Voyager episode?) where Tuvok, at a time when he is assigned to an Excelsior class, rooms with three or so other officers. In Star Trek: Strange New Worlds, Ensign Uhura is shown sleeping in a wall bunk as well, though she at least has a room. The point is, none of them had much private, intimate space to themselves.
There is one place on the ship that has been mentioned a few times regarding these...issues.
I distinctly recall a scene in Lower Decks where Beckett Mariner is assigned holodeck cleaning, and she complains about people "doing that" in the holodeck. In Star Trek: Deep Space Nine, there are the "holosuites" where Quark peddles nefariously-obtained holographic fantasies to customers.
So then, is the holodeck where..."it all happens?" Are there any other places where lower-ranking officers could make it work? Or do they have to sneak off to some secret corner in the Jefferies tubes to do it? Unless the whole crew gets infected with some sexy virus and suddenly starts engaging in public indecency (see TNG: "The Naked Now" and LD: "I, Excretus"), in which case the need for privacy apparently vanishes, but let's not talk about that.