In South Australia, it is a criminal offence to have sexual intercourse with a close family member [Criminal Law Consolidation Act 1935 (SA) s 72].
A close family member means
It does not include a family member related by marriage or adoption alone.
The maximum penalty for this offence is imprisonment for 10 years.
Consent is not a defence to an offence against s 72. A defendant who can establish that they did not know, and could not reasonably have known,that the person they had sexual intercourse with was a close family member will have a valid defence [s 72(2)].