When your a GM, you want your players to feel invested in their characters, at least for the long term play. Investment breeds attachment to both personal characters and NPCs. Should you want to create an attachment, you have produce an emotion through a reactive event.
Example : Two ally NPCs fall in love. A player character uses Insight and Perception checks to sense that they stare at each other often and will speak to each other in private, having small trysts when they think the party isn’t around. I use small words to describe their relationship, rather than large ones, to show the relationship is new but the bond is strong! The reactive event is when they are embarrassed when they are figured out, as they thought they were being private about their relationship.
Mechanically, the two NPC’s act on the same turn, and receive bonuses to rolls when they are near each other, but if one is harmed to much, the other dedicates their turn to helping them (instead of a valuable party member). Another obvious clue of their bond
Players would sense their connection is valuable and should it be severed, there would be a consequence. Players might protect this bond, or create strife inside of it to see the unfolding drama.
