The premise of this book is the experience of a human man on a planet where the people are neither male nor female and who go into a type of "heat" once a month. Incestuous relationships between siblings are acceptable unless a child is produced from their union, after which they are forbidden to continue their relationship. These types of relationships are explored as tales within the larger narrative of the book and as a practice one of the main characters participated in in the past. We are invited to assume that the relationship between that main character and their sibling was one of love and to also feel sorry for the siblings for being forced apart after they had a child together. It is not directly stated but implied that both siblings may have eventually commit suicide in grief at their separation.