Requirements for the list: 1 woman in a relationship with two or more partners. To fit the criteria the men must be in a 'relationship' with the woman, so not only sexual. Next, the men should know of eachother and be accepting of the relationship/s by the end of the story.
Important: not all of these are created equally, some of them lack plot, character, or art. Sometimes they are trash.
On another note: I'll have a secondary watch list for non confirmed reverse-harem (they are implied but there is no concrete relationship yet). I will also be adding as I read/confirm other stories.