Harry had known Ron since he was a baby, they'd grown up together. Apart from Minnie they were the best of friends. They met Hermione on the train, she was a bit nerdy and her hair was like a birds nest but she was super smart.
He had inherited his dads need to cause trouble, Ron was game for anything while Hermione helped point out the flaws in the plan. She thought she was discouraging them. Such a silly girl!
They fought like cats and dogs sometimes but they were the closest thing to family he had with him.