various suggestions for sources of pre sentience interaction/relationships:

the guilds description mentions that there was a fair bit of rp going on which could have involved the npc's creators using them as chars in one of stores or entire campaigns or ongoing narratives that could have been incorporated into their memories. 

You also have the various npc/item descriptions 
their own descriptions could sate that 2 npcs are friends, lovers, rivals, siblings etc 
the descriptions of their environments/floors could include flavor text mentioning meetings ("graft regularly holds meetings with the other guardians in this board room" or "The lawful denizens of the chateaux often come here to pray with Aurora")
The descriptions of mobs ("After Kaldorna began assisting Gromgard with the training of these goblin wolf riders only 30% of the goblin trainees where eaten by their mounts" or "after repeated thefts of her precious tombs Kath commissioned Ashara to scatter these book shaped mimics in her library")
weapons and items could be gifts or collaborative projects.