The Creation Kit allows users to set NPCs' dispositions toward others. ... and themself, for some reason.

This is what causes the hired thugs to come after you when you attack someone who has a positive disposition with someone else, or letters saying "thank you for killing that guy that i hate" after you kill a guy that someone hates. Depending on how much they like someone, an NPC may be more inclined to assist them in battle... there are probably other things I'm forgetting.

I-wouldn't-say-plenty NPCs already had relationships with each other, obviously, because I'm sure you've experienced the aforementioned moments.
BUT!

I said, not enough. And so, I set out to provide more relationships between NPCs. And now, after getting through a mind-numbing amount of Late Night With Conan O'Brien episodes from before I was born that I had playing as I sifted through UESP and decided (in a hopefully reasonable manner) who was friends with who... here it is. The result of my work. Can you tell that I'm tired yet?

586 relationships across 397 NPCs, according to xEdit. I don't really believe that. I'm probably reading it wrong. I'm tired. But it's good advertising?

I, uh, I'm not sure quite what I've released. I wanted to get this out. I probably won't be doing a playthrough of Skyrim for some time, so I can't test this.

First of all, when I asked on reddit right before I started this I was informed that, due to Bethesda's infinite genius, editing NPCs at all will mess with NPC appearance overhauls. Then I was informed that this wouldn't. And if you do it correctly, which I didn't (it's fixed now!), well, it shouldn't. This shouldn't. Mess with NPC appearance overhauls.

You'll probably also be spammed by letters now but enough people are running Anniversary Edi-

FAQ

Where do I load this?

As high as possible. ... as low priority as possible? Before any other mod. Even the unofficial patch. On that note (well, I'm assuming, anyway):

Does this change any relationships Bethesda already set?

No.

... and trust me, there are some weird ones. There are like two daughters on Solstheim set as being lovers with who is supposed to be their father. And don't even get me started on what the Battle-Born family tree looks like.

Can you explain your decisions?

Haha! No! As I said, I read the Unofficial Elder Scrolls Pages Page for more or less every named NPC. Cities and other settlements provide a neat list. BUT! The UESP is not an authority in any way. I did not adhere to what the UESP said if I could not find evidence for it. For example, there are pairs of NPCs that the UESP refers to as husband and wife, however, I could not find any actual evidence for their relationship. They could be siblings, or really good friends, or something, so I set them as Allies of no particular type. ... on that note,

I think you made a mistake, and I have evidence to corroborate.

By all means, let's hear it. I may be tired of this mod, but I still want it to be as good as possible.

I have a suggestion for a relationship!

No, I'm not giving Nils and Sigurd a relationship with each other because something funny happened involving the two of them.

Your mod RUINED my save!

I mean, I don't believe you, but uh... sorry?*

*Wikipedia says my province has a similar law to one in Ontario that says saying sorry is not an admission of guilt!

Your mod has caused a more believable issue or it really did genuinely ruin my save somehow!

I'M SORRY! I'M SORRY! I'M SORRY! Bug report NOW!