In the latest incident, he is said to have raped his eight-year-old sister in an empty house in Sungai Layar here after dragging her from their own house next door at about 8pm on Wednesday.
The girl told her 39-year-old mother about the incident at about 9am yesterday despite being threatened by her brother not to tell anyone.
Her mother, who is unemployed and has 12 children, lodged a police report here at 5.50pm the same day. Her husband is a labourer.
Kuala Muda district deputy police chief Supt Saifi Abdul Hamid said initial investigation revealed that the suspect had also raped two other sisters, aged nine and 14, in the past.
He said the two girls also informed their mother about the rapes but she did not lodge a police report as she thought it was a prank since her son denied wrongdoing and told her that the girls were slandering him.
He said the suspect also denied it when the woman questioned him about the latest incident.
Supt Saifi said the suspect, who is jobless, surrendered himself at the Kuala Muda district police headquarters at about 10am yesterday.
He said the youth tested negative for drugs.
"All the three victims will be sent to the hospital for examination," he said in a statement.
He did not state when the other two girls were raped.
Supt Saifi said the case would be investigated under Section 376B of the Penal Code. The offence carries a jail sentence of 10 to 30 years and whipping.