Who was Jane Austen's only sister?

Cassandra Elizabeth Austen (9 January 1773 – 22 March 1845) was an amateur English watercolourist and the elder sister of Jane Austen.

There is little biographical information about Jane Austen's life except the few letters that survive and the biographical notes her family members wrote. During her lifetime Austen wrote approximately 3,000 letters but only about 160 survive. Many of the letters were written to Austen's older sister Cassandra, who in 1843 burned the greater part of them and cut pieces out of those she kept. Ostensibly Cassandra destroyed or censored her sister's letters to prevent their falling into the hands of relatives and ensuring that "younger nieces did not read any of Jane Austen's sometimes acid or forthright comments on neighbors or family members." Cassandra believed that in the interest of tact and Jane's penchant for forthrightness, these details should be destroyed. The paucity of record of Austen's life leaves modern biographers little to work with.

The only known portrait of Jane Austen was drawn by Cassandra.