Answer:
Readers can sympathize with Antigone because of her compassion. Antigone doesn't see the ties of blood, love, and respect as ending with life. She asserts that she has no chance of having another brother, because both her parents are dead.
Antigone also considers that she will spend much more time dead than alive. So she must think of how she treats death and the dead. She feels the additional responsibility of being the great great great granddaughter of Cad mus, who founded the city of Thebes in about 2000 B.C.E.; and the great great great great great granddaughter of Poseidon, the sea god.
With such an ancestry, it isn't surprising that she wants to be in compliance with the enduring legacy of the gods, and the equally enduring traditions of Thebes' founder.