Got me thinking about what it means for a harem to make sense storywise... Or what it means for a harem NOT to make sense, for that matter.
You didn't say anything agains incest, so... What comes to mind is the series of games by Lockhart. "A Petal Among Thorns" is the first one, it is one-on-one essentially (MC and LI), but is the beginning of the process of building a harem around the MC. The next game is "A Moment Of Bliss", it sort of ends up in most of the harem built. There will be further game(s) in that "universe", united by the same characters and the very premise for a harem which is revealed in the 2nd game. All of them are exceptionally well written by someone who actuially knows more than a thing or two about feelings and empathy.
Not a single drop of jealousy in those games though. For the same reason/premise that explains the harem in the first place. Telling more would be a spoiler.
Some more lighthearted examples could be Snow Daze, Power Vacuum, maybe even Parental Love (too much of a fuckfest to be "realistic" imho)