Neil Bantleman, of Burlington, Ont., was arrested in Jakarta in mid-July during a police investigation into the alleged sexual assault of three kindergarten students.
Bantleman, who worked at the prestigious Jakarta International School, was detained along with an Indonesian teaching assistant and both men have denied the allegations.
Guy Bantleman said Friday that his brother was handed papers Thursday night telling him he'll be spending another 30 days there.
He says his brother has yet to be charged with anything and is being held with no evidence, adding while the family expected the detention to be extended, they are still shocked and disappointed.
Guy Bantleman says he believes the extension is being done to make it appear the police have done everything possible in their investigation.
"The police really didn't have to do what they did as far as detaining Neil," he told Hamilton television station CHCH.
"So it's almost like you have to let the police extract themselves from the situation they put themselves in and they have to be able to save face."
"They need to be able to say we've investigated thoroughly and there is no evidence there and is no issue that occurred. My assumption is that will go on for another 20 to 30 days," he said.
"They can't hold him for more than 120 days so we are halfway there and the other is the file can't go back and forth between police and prosecutor more than three times."
He says his brother has met with Canada's ambassador to Indonesia, who assured him his case is high priority.
Indonesian media reports said the police investigation began with the arrest of six outsourced cleaners in connection with allegations a boy was raped in a school bathroom in March.
The Jakarta Post reported that the parents of two other students filed police reports claiming their sons were sexually assaulted by teachers.
Neil Bantleman and Ferdinand Tjiong were brought into a Jakarta police station for questioning on July 14 and detained the next morning.
(CHCH, The Canadian Press)