Honestly, this one's hard. Most of my characters don't "live in a specific world". SO I'll probably be writing some pieced together things since most of my characters are pretty on their own. Friendship is an interesting topic to talk about among characters.
Section 1 "The Trio who knows my own OCs" If I would go by "Character with numerous connections to my other characters" then it will have to be the trio Dragon, Tapix, and Corvex. This trio is the only set of characters to end up knowing other characters of mine through meeting and storytelling as extensively. It's a trio that ended up creating their own universe (that I don't right about) and create their own relationships between a number of my other OCs.
They've traveled their world, met with enemies, met with friends, and have many aquantences. Dragon in particular, who also knows my Music OCs Rone, Tanto, and Toni through meeting up at a cafe.
Section 2 "Those two who hang out with other's OCs" If we talk about "Characters who know a lot of other characters" there is no other OC of mine who isn't as frivilous to meeting people as Sin. He's a character who actively seeks out other characters. He was made as part of DnD first, meeting an array of others in game to start, then as an OC knowing the "Misc Universe set" of my main characters, and also hanging out around all of you guys. Ah, but it would be a bit much for me to say he has "friends" more than that he just knows a lot of people. Stretching the term friend beyond the length of laffy taffy here.
In second place there is Uluri, my persona and the OC who has to go out and meet other people's OCs. Uluri, although my persona, is also a Character as well, and as such does get to go out and meet a lot of different characters. Uluri knows a handful of my Own OCs, lives with a Trace, visits Kindling, puts up with Sin, has met with many other people's OCs. Their life is ultimately effected heavily by all of you viewers as well.
Section 3 "The Friendliest Character" Hands down it's Kindling. If there is a character that I would say represents friendship, it would be this cute little ball of wax here. He hasn't met a lot of my own characters, or interacted with many of you guys, but when he does it is hospitality at its finest. A greeting and an offer for food, a character who will listen, and someone who goes out of their way to make sure that everyone feels comfortable.