Hi.
my partner has been offered a job WA, we are unsure the company will sponsor a family visa. If this is the case.. what visas would me and our child be applying for?
many thanks

If they are sponsoring him, then you and the child will go on that visa as dependents. They wouldn't be sponsoring him or you on a family visa, as that doesn't exist. They will either be sponsoring him on a temporary or permanent skills visa, with you as dependent family.

Otherwise you would need to wait for him to be established on a permanent residency visa, then sponsor you both to join him on a Spouse/Partner Visa. Can take a couple of years and is very expensive.

To be honest, if you are a de facto/married couple, with a child, and they refuse to add you to the application, then they really don't know their way around Aussie visa!
Do you know what visa they are sponsoring? 190? 482? 186?

The company do still need to sponsor the dependents as well as the primary applicant, but any company that won’t do that for a family should probably be given a wide berth anyway.

Your family would come as a package, so you would all be on the Visa I would assume.

This can only happen if the sponsor agrees to sponsor the family - see Paul's reply above.