The following is said in the “general” sense, and not in the “absolute” sense, but it does apply to the majority of fae.
We just don’t have the same hangups mortals have. Not with gender, where it even applies. Not with partners, or other races, or the number in the relationship.
I have known some fae that feel jealousy or are monogamous but this tends to occur with sidhe and more ‘courtly fae’, and even uncommom there. Its rare in nature fae (like brownies, sprites, lamia, satyr, mercreatures, etc).
The world is filled with stories of love between mortals and fae, relationships between us were once, while not common, not unusual either. As the world became more “abrahamic”, this became less common. There are still mortal bloodlines with fae blood in it. Many times these relationships failed however, partially because of an expectation of exclusivity.
Fae in general do not feel they “own” or “possess” their partners. Even the Sidhe who may engage in monogamous relationships, or specify someone in their life as a spouse, they still do not feel this and the relationship is generally what mortals would consider “open”.
Orgies.. well they happen. But its more common for fae to form relationships and create a familial group out of those they love. There is a measure of loyalty in this group, but not in the mortal sense. Mortals measure “loyalty” in whether one does not have romantic feelings for others, Fae measure it by whether or not existing relationships are broken over them.