On 16 June this year, he attacked his 15-year-old sister.
She was sleeping in her bed in T-shirt and shorts when she felt someone grope her right breast.
Opening her eyes, she discovered her brother standing in front of her naked.
She shouted at him to leave her room and he apologised.
He had been aroused seeing her sleeping, after exposing himself to her a few days earlier.
Then, he was at home high on alcohol and sexually aroused, and he stripped naked and asked his younger sister to touch him.
She told him to put on his clothes and walked off.
Pervert Bro also attacked his other sister two years ago, when she was 17 years old.
Operating in similar fashion, he touched her breasts when she was sleeping in her room.
After the latest incident this year, the girl made a police report on behalf of her younger sister.
In court, Pervert Bro said he had made many mistakes and regretted them.
He said he was prepared to accept punishment for his actions.
He will be sentenced on Monday (3 Oct).