I'm from the UK and moved to the Aus to be with my now wife.

First thing, have you lived together for a year? I'd guess not, so the partner visa probably won't work (we were long distance for 2years, had Skype records, flight tickets etc and it didn't help, and cost us money)

Are you on the child's birth certificate? If you are you might be able to get the partner visa.

If not, this is what I would do:

1: get a working holiday visa to Australia (pretty easy to do, and what I was advised to do by immigration)

2: live together in the same address (get joint tenancy, joint bills, and a joint bank account) the paper trail helps.

1. Make some joint friends (you will need some reputable people to do statutory declarations)

4.take photos together.

1. After about a year together apply for a partner visa (each Australian can support one person coming into Aus this way)(also look into registering your relationship as a defacto)

2. Either get married or spend 2 years on a probationary partner visa. After the 2y you get permenanat residency.

I would get an immigration agent. Depending where you will be in Aus I can recommend one in melbourn if you pm me.