Apple One signed up with an Indian account, can not be family shared with AU account. The only thing that be shared with AU account is iCloud storage as far as I know. Services would not work on iPhone/iPad if you want to continue using your current Apple ID for purchases.
It's a good deal for Apple TV users to be able to access Apple Music, Apple Arcade, and Apple TV Plus, while also being able to share iCloud plus storage with their AU account.
Set up an Indian Apple ID using your AU number to verify.
Login into an iPhone, iPad, iPod touch, using an Indian Apple ID.
Buy Apple gift cards from Amazon India using your AU amazon account. Enter an Indian address (make sure indian address is selected, otherwise it will show as out of stock) and use a virtual card from Wise. Sometimes it shows gift cards out of stock when logged in with AU account. Try again and see what works for you.
Sign up to Apple One via settings.
Login on your Apple TV as a second account and enjoy all the services for a lesser price.
You can also share the iCloud store with your AU Apple ID via Family Sharing
Yes it can…
https://support.apple.com/en-au/HT201060