"You're my third oldest friend and you fucked me like a tied goat" — Kendall to Stewy
Kendall meets Tom on his first day of Junior High. Tom is one of the older boys tasked with welcoming newcomers to the school and he takes shy, stuttery Kendall under his wing. Tom is not really a fighter, but he's tall enough that just having him at Kendall's side is enough to ward off bullies.
Tom is very interested in Kendall and his family. Some people call him a 'climber', whatever that means. Some of them make fun of him behind his back for his family's rural background. His grandfather owned a farm. His parents are both lawyers now so he's comfortably off, but not as rich as most of the boys in the school.
Kendall brings Tom home once to spend the summer with his family. Tom plays in the tree house with Kendall and Roman and poses for photographs with them and Shiv, which will probably end up in one of his dad's magazines.
Logan doesn't take much notice of Tom until they all end up playing The Game one afternoon. Kendall has always hated The Game and usually finds excuses not to play. After Tom hits a home run, knocking Kendall out of The Game, Logan pats Tom on the shoulder and says Well done, son.
Kendall doesn't invite Tom back to any of his homes after that. Their friendship gradually gets phased out, until Tom and his family move back to Minnesota.
…
He meets Nate in his last year of High School. Nate is the best-looking guy in school and Kendall is intimidated by him, despite being a few years older than him. They meet in one of the many after school clubs that Kendall joins to get away from Logan, this one being music club. Being Scottish Logan approves of music, despite his fear of his sons turning out 'faggotty'.
He and Nate write songs together while smoking weed and talking about liberal politics. They stay in touch over the years and end up partying in Shanghai together.
On returning from Shanghai, Kendall introduces Nate to his family and Nate gets the Logan Roy nod of approval. Nate is tactful or savvy enough to keep his political opinions to himself in front of Logan. Eventually he asks Kendall Would it be cool if I asked your sister out?
…
He and Stewy meet in the first week of Harvard. Stewy is one of the few people there who is almost as rich as Kendall. It turns out they both went to Buckley, albeit in different years. Stewy introduces Kendall to a world of drugs and women, and has none of the billionaire's guilt that Kendall has. "Just enjoy it, dude," is his constant refrain. Kendall knows that there are many more socially skilled people that Stewy could be hanging out with, but Stewy remains at his side. "Team Ken, baby!"
He brings Stewy home for Thanksgiving and Stewy immediately gets into a war of words with Logan, calling him a 'walking hate crime' to his face. Roman and Shiv seem to like Stewy, or are amused by him anyway.
"What an obnoxious cunt," Logan says as soon as Stewy leaves. "Please don't bring him here again."
Kendall smiles inwardly and thinks yeah, I've found my best friend.