...due to an understanding of what it must mean to be the eldest (not to mention only) son of a fine family? Charlotte may not be forgiving of deficiencies in a person of wealth but realize that Darcy's upbringing may have given him a higher opinion of himself than outsiders such as the folk of Meryton would form of him. Even in Charlotte's family she may see the different indulgence toward the eldest son and the opinion such a son would have of himself. We can suppose that the boy who accompanied Charlotte to visit Longbourn would be one of the elder, if not the eldest son, in Charlotte's family; and he seemed much more outwardly self-satisfied than Charlotte (or Maria) was.