Michele Mongelli, 64, a scrap metal dealer, and one of his sons, Giuseppe, 41, have been arrested on suspicion of rape and sexual abuse and face up to 20 years in jail if convicted.
The woman, now 34, alleged that her father was 'a sort of husband' and her brother 'a sort of lover'.
"When I was 16 years old my brother took my virginity," The Telegraph quoted her, as telling during a three-hour police interview in Turin.
The two men fought over her 'as one would argue over a prostitute', she claimed.
She added that she was treated like a slave and was forced to sleep near her father's bed, so that she was always 'within reach'.
At 13 she stopped going to school and spent most of her time in a darkened room packed full of cuddly toys, she revealed.
According to the country's police, the older man 'groomed' his son as a sexual predator, and that Giuseppe went on to sexually abuse his own daughters, now aged six, eight, 12 and 20.
The case draws many similarities to Austrian incest case of Josef Fritzl, who raped her daughter Elisabeth for 24 years and fathered seven kids with her.