Sirius continued to grin and leaned forward a bit, levering more of his weight down on James so that he could keep him in place. He knew that James wasn't seriously trying to break free -- he could have at least rolled Sirius if that had been his intention, but Sirius didn't really mind the halfhearted attempt for the time being. He was sore as well.
"Merlin, that wouldn't have been hard," Sirius answered readily. "Walburga never let me and Regulus have sugar at that age. First hit and we would have been off the walls." Perhaps his mother had been trying to calm down an already rambunctious child, but Sirius was fairly certain that she just never wanted them to experience anything nice in life.
"Was he a pint-sized greasy tosser?" Sirius asked -- because even if James might have been willing to try and be an adult about Snape being a part of their lives, Sirius saw absolutely no reason to. He didn't like Severus Snape and that was the end of it in his mind.