The one specific clue that you get in the novel is that his father was a commander in the navy, and if you look into life of officers in the British Navy, even that of a commander isn't necessarily going to translate into a life of luxury. Of course this would also suggest that his father would have maintained strict discipline in the home which can also be tough for a young boy, though for Ralph it has clearly left him with a respect for and even some need for a recognized authority and for rules and regulations.
Ralph is also clearly used to disappointment as he seems to even expect failure from the very beginning of his attempts to lead the boys. This is particularly clear in comparison to Jack who seems to possess a very natural charisma that Ralph lacks.
I'd say you can tell this by the differences between his reaction and Piggy's reaction to the idea that no one is coming to rescue them; he seems almost to expect it. I'd also say you can tell this simply by how harsh he can be, and how willing to shut out others' concerns. He simple goes for what he wants and leaves their concerns behind; he is not emotionally open. (This can be seen even in the novel's first pages.)
He was left alone when most of the boys left his group for Jack's group except Piggy, leaving him alone to defend against Jack's group as his former boys had succumbed over to survival instincts and defect to another group