@jowin18 - congrats po..
@nfronda is correct, because your agent did not include your family while the visa is in process, you will need to re-apply for them, and of course pay another fee..
i think the main reason is because there is already an employer waiting for your in AU.. and including your family in the application might delay the process in terms of police clearance and/or medicals being referred.. it can happen that medicals for kids can be finalized only after 6 months of waiting.. if ever that happens, then your visa will get delayed.. and even worse, your employer might back-out after waiting for so long..
so just look at it on a positive note.. you have your visa,, a work now... sisiw na lang ang application fee sa inyo..