Jim McDougall said Simon Kadwill, an Englishman, had lured his daughter, Chantelle, 27, and granddaughter Leela, 6, away from family and friends.
The trio, along with flatmate Antonio Popic, 40, were all living in a house in Nannup in the state’s southwest and have not been seen or heard from since July last year.
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Kadwill is the author of several books predicting the end of the world including Servers of the Divine Plan and The New Call.
Mr McDougall, who lives in Albury, said he believed Kadwill had tricked his daughter into believing the end of the world was near.
“He probably has a long string of woman all around the world he has done the same thing to,” he said.
Brett Mitchell, owner of Esoteric Publishing which published Servers of the Divine Plan, said Kadwill wrote the book about the birth of a new world but denied he was a cult leader.
“This publishing house was founded to help people find their own way to truth, not to support cults and other fanaticism,” Mr Mitchell said in a statement on the company’s website, dated April 2.
“I’m removing the book from publication immediately.”
Ms McDougall last spoke with her parents on July 14 when she told her mother they were going on a trip to Brazil. They have not been seen since.
The bank accounts of the three adults have not been touched since and immigration checks have shown they have not left the country.
Mr McDougall believes Kadwill had planned to take his daughter.
“He was a smooth guy. Not someone I liked,” he said.
“They have done a runner because they left the house with the food in the fridge.
“They planned it, they obviously planned it.”
“We have investigated it and it hasn’t been substantiated,” Ms Weatherall said.
“They are a little family unit. It is not illegal to go missing but it is nice if you let your family know.”