The most frequent examples in Austen of shared emotion involve the depiction of siblings, another affirmation of Hume's contention that we are naturally inclined to sympathize most with those to whom we are closest. She stresses the importance of fraternal ties, even over conjugal ties: "children of the same family, the same blood, with the same first associations and habits, have some means of enjoyment in their power which no subsequent connexions can supply (MP 235). A brother or sister is someone with whom "every former united pain and pleasure [can be] retraced" (MP 234). Such a unity of past experience and recollection facilitates a continuing unity of feeling. In Sense and Sensibility, even the usually restrained Elinor shares Marianne's distress about Willoughby's desertion and gives way to a burst of tears, which at first was scarcely less violent than Marianne's" (SS 182). Catherine Morland weeps in sympathy with her brother's disappointment as she reads his account of Isabella Thorpe's perfidy (NA 203). Fanny Price's sister Susan "was always ready to hear [Fanny] and to sympathize" (MP 428). It is said of Jane and Elizabeth Bennet of Pride and Prejudice that "each felt for the other" (PP 334).
E. M. Dadlez, Mirrors to One Another, pp. 82-83. Austen herself was on excellent terms with her siblings, which probably accounts for the prominence of sibling relationships in her work. She spent an immense portion of her life with her sister Cassandra, and after the death of her father, she, Cassandra, and her mother lived for several years with her brother Francis, then afterward moved to a cottage on the estate of her brother Edward. Her relations with most of her other brothers -- Henry (who seems to have been her favorite brother), James, and Charles -- seem to have been fairly close, as well. (She had another brother, George, but we know very little about him, beyond the fact that there was something wrong with him, and it has been thought, based on a few scattered evidences, that he might not have been able to speak, so that he was sent away at a young age to be cared for. We know the family paid for his upkeep until his death in his seventies , but we have no indication of any other connections. He certainly would not have had "the same first associations and habits".)