Romance wise, they're fairly tangled up!
An example I can say off the rop of my head is Syldro and Erinek being very close, ever since they were little. Syldro was a welcome level of protection before they entered the game, and Erinek sometimes had to stay. Syldro is also the reason everybody knows Owenne and Lynneh, and why those two are still alive!

ailean, everet, eugene, and pedrii are all connected in the same timeline so their backstories are all tangled up w each other

-squints-
Kro, Poriva, and Gamzee are all pretty closely linked what with being in the same timeline and two of them being in the same household.