Hi, according to Wilks family word-of-mouth, Joseph Joseph Wilks is buried in an unmarked grave in the Jewish section of Stawell cemetery in central Victoria.
Also according to family word-of-mouth, the Josephs are Spanish in origin. An older family member is recalled to have said the family were called "marranos", a derogatory term used in the past for Spanish Jews who were thought to have pretended to convert to Catholicism.
Also, I have read that the Spanish custom for giving children names is to give them their own Christian name then their father's surname followed by their mother's surname, hence Joseph Joseph Wilks. Family members still have the Joseph Wilks surname although usually the 'Joseph' is silent with just 'Wilks' being used for everyday purposes.
Although hearsay, it is interesting and opens a new avenue for searching. Hope it helps.