How did that parent become an Australian citizen?
Australia — Citizenship by Descent
This decides whether one extra condition applies to you. A parent who was themselves a citizen by descent has to have lived in Australia for two years; a parent who was born there, or was granted citizenship there, does not.
They were born in Australia → They were granted citizenship while living in Australia → They were born outside Australia and got it through their own Australian parent → Some other way, or I'm not sure →
Question 3 · start again