Kenny hasn't talked to hide friends for a long time. The last time he had talked to his friends was that last day of high school, which was around 2 or 3 years ago. The most he communicated with them was occasionally sending of a meme in their gc. 

Butters is a sweet, respectful, kind dude who is Kenny's best friend.

Cartman is rude, rarely feels sympathy, but sometimes kind.

Stan is monotone, kind, and Kyle's best friend.

Kyle is a sweet but easily angered dude who is Stan's best friend.