Immigrationboards.com

Background
Mother - Born in the UK/British citizen (Moved to Australia with her parents when she was 4, never had a British passport)
Mother's parents both born in the UK/British citizens (both deceased, we have all their papers)
Father - Born in Australia/Australian citizen
My sister and I are both born in Australia.

I am 17 and my sister is 14. Can we both just apply for a british passport or do we need to be registered before we turn 18 first? I turn 18 in a month and the information online is confusing.

If we do just apply is just sending my mother's birth certificate enough or will we require my grandparents information as well?

Thanks for any help.

Were your parents married?

If you were born after 1 Jan 1983, you are automatically British by descent and can apply for a passport directly.

Thankyou for the quick reply!

My parents were married when my sister and I were born but aren't anymore. So would just my mother's birth certificate be enough when we apply? Or will we need the marriage certificate and my grandparents papers too?

You should follow the passport guidlines/booklet.

Mothers birth cert and marriage cert to show name change. Grandparents might be useful if you have them but they are fairly easy to get and you will need your birth certs.