This is just a really short blurb based on a tumblr post I saw
Ever since Tartarus, Percy got really close to all of his friends.
He'd sit really close to Will Solace, their shoulders touching. He'd hold hands with Connor Stoll whenever they were around each other. He'd cuddle with Jason - sometimes throughout the whole night. He'd curl up with Piper and they'd play with each other's hair. He'd spend nights in Bunker Nine, leaning his head against Leo's shoulder as he tinkered away on his machines. He'd hug Nico whenever he saw him, and it always lasted a longer than a regular hug would. He'd lay his head in Hazel's lap and let her play with his hair. He'd lay with Annabeth and played with her hair. He'd curl up with Frank - usually when he was in the form of a dog - sometimes when he wasn't. Sometimes he would get a few of them together and they'd all just cuddle up to Percy.
It wasn't romantic at all - just platonic. It was grounding for Percy, it let him know that he was there with them and he was safe.
When he'd wake up from a nightmare, there was always someone there to wipe his tears and hold him and reassure him that they were there. That they always were going to be.
Sometimes he switched it around; held hands with Jason or laid his head in Franks lap. Whatever he needed, his friends were there to give it to him, whether it be a hand holder, a cuddle buddy, or someone to play with his hair.
It was his way of coping.