It probably really should have occurred to someone, Ron thought in bemusement, that it was their fault. The reason Percy stayed to himself among the family was simply that no one ever actually asked him to do anything; no one ever even tried to involve him. He must have once tried, but eventually Percy had started to give up - he must have felt as if he were unwanted. It wasn't as if they'd done anything to discourage the feeling. Thereafter, Ron resolved not only to study with him, but to play chess with his brother more often. Percy was a better opponent than any of his three dormmates, after all.