Yes, Maud Louise's birth certificate should have both parents' names and other information, as should the bapt for Augustus on 2 Oct.1870 Saint Barnabas, Douglas - although only her mother's forename may be given in the latter entry, as recorded in the IGI. Both should have father's details, address and occupation.
See "Contacts" at www.gov.im/registries/general/civilregistry/

From what you wrote about the "Indenture of Settlement in favour of Mrs. Susan Fynney" it looks as though the brother only discovered her existence after Augustus's death, and it would confirm that Susan's children were indeed his. She must have approached him after the admin. of Augustus's estate (see my last message).

That seems to tie it all up very neatly, with the only questions being who registered Albert Dixon as being their father, and you will get that from the birth cert. And who he was, if not imaginary?

I had a look at the archived messages to which you referred, and it was a pity you answered Brian in 2010 (who had died) rather than the person who started the thread and who was related to Maud Louise - or did you manage to contact him?

Do you know which Australian state Augustus was in, in 1855? Was he Augustus or Caesar? All states keep their own records separately, unlike England.

Sue