An overwhelming majority of the child victims in sex crimes perpetrated by a family member were aged 13 or younger when they were first victimized, a parliamentary report showed Sunday.

The National Assembly Research Service compiled a report based on its survey of the four juvenile protective facilities for the victims of sex crimes by family members, which were established in 2010. Of the 316 children and teens currently under protection, 115 -- or 36.4 percent -- were first subject to the crime when they were 10 or younger.

The numbers of children victimized at the age of 11, 12 and 13 were 55, 45 and 33, respectively, meaning that 78.5 percent of the victims were aged 13 or younger when they were sexually assaulted.

But the report showed that only 17 children were admitted to the facility when they were 10 or younger, and 81 when they were 13 or younger. This shows that for most victims, there is a substantial time gap between when they were first molested and when they came under the protection of authorities.

The report pointed out that this implies that the child victims were exposed to sexual violence for extended periods of time.

While 316 child victims were victimized, there were 338 perpetrators who inflicted such damage on them. This is because some victims were subject to sexual violence from more than one person.

More than half of the perpetrators were the victims' biological father -- 58 percent -- followed by older brother (14.5 percent), stepfather or the man living with their mother (12.7 percent) and relative (6.8 percent). They were punished in 174 cases, 33.3 percent in which the perpetrator was sentenced to a prison term between five and 10 years.

The report showed that the majority of the children were left unprotected by their mothers, possibly linked to why so many of them were subject to sexual violence by their fathers. In only 24.4 percent of the cases were the children's mothers married, and in 52.2 percent of the cases the children were not being cared for by the mother due to factors like divorce or the mother falling out of touch with them.