With this system, either with new NPC or legacy, if possible, how would be the best way to establish 'ties' with the player or protagonist from the get go? Adding some delicious lore nuggets or even establishing they have been a resident for a while could be fun.
For example, let's say they are a new guard to bolster the ranks with Darian. Would writing something like 'playername is a recent hire in Silverpine to guard the town borders' do the trick? ...Though I imagine this would have to be done with nearly every Silverpine resident to make sense.
Or if establishing familial bonds, player is a cousin of x?
Before the no modded images rule, this is EXACTLY what I was doing. I’ve added a apprentice guard for Darian and made a very very janky patrol routine to cover the day shift which I’m still refining. It’s put in the character description he’s still new, clumsy and slightly insane and everyone just accepted it very easily. Hayden now lives in constant nervous wreck mode as the apprentice has declared him his new ‘best friend’. It’s great.
In Set Knowledge, you can enable if the knowledge you created is Public. If you leave the box unchecked, then I assume it's Private and only that NPC will know the knowledge. Public, I assume means every NPC will have access to knowing it. So you DON'T have to mod every NPC.
So, if I had to guess, and using your example as a means to explain it:
Your player character can be a new hire by slightly modding Darian by adding, "%NAME% recently hired someone new to help him guard Silverpine", to his Knowledge set. If you want your player to be related to Darian as a cousin, add, "%PLAYER_NAME% is a (optional: close or favorite) cousin to Darian." as another Knowledge set. Let the LLM put two and two together naturally and dynamically decide if he hired his cousin either as a coincidence or intentionally. Edit the knowledge if you want one or the other. Just make sure any lore about your player character's relationship with an NPC is NOT PUBLIC and increase relationship with them to whichever one gives you the key to their house so you can enter anytime and place a bed down to sleep. Probably Important, but if you're cousins.
Remember that public knowledge is only knowledge known to NPCs who personally are acquainted with that NPC, so usually you want a NPC everybody knows (that would be Gareth) to be the holder of the information, or to make your own NPC who somehow is acquainted to everybody, they don't even have to be in Silverpine either, just to 'exist' within the world of the game, so you can make it up and give it coordinates that are out of bound or something.
It's mentioned as a tooltip of the public knowledge toggle when you hover on it.
It's made to be logical; if the NPC hasn't even met the NPC 'holding' the knowledge, how would they know about it?
So basically the other NPCs need to be at least acquainted with that NPC to be aware of the information they hold.
It's quite easy to test and verify as well, try speaking to Mirel about Orson or a hunter in the woods, and she won't have the single-est clue about whoever you're talking about; Gareth knowledge of Orson is private, he just knows Orson personally and Orson delivers him meat every Tuesday, and they're aware of eachother, but neither Celandine nor Gareth hold any public knowledge of Orson, so when you mention Orson to Mirel she just goes 'Ors- who?'.
That is of course if Mirel hasn't met Orson directly due to somehow having both of them in a conversation because she lives with you or something, because otherwise their schedule makes it normally impossible (as far as I'm aware) for both of them to be in Gareth's tavern simultaneously.
If you talk about Isolde to Gareth however, (a personal herbalist friend of Rosalyn, that lives off-screen in the capital and is the person she visits every time she goes out of town) because that is public knowledge of Rosalyn and anyone that knows her, he'll immediately understand what you're mentioning.
To sum it up, yes, it is quite organic and elaborate, and you need to keep track of these interactions as well.