Incest between a child or adolescent and a related adult has been identified as the most widespread form of child sexual abuse with a huge capacity for damage to a child. One researcher stated that more than 70% of abusers are immediate family members or someone very close to the family. Another researcher stated that about 30% of all perpetrators of sexual abuse are related to their victim, 60% of the perpetrators are family acquaintances, like a neighbor, babysitter or friend and 10% of the perpetrators in child sexual abuse cases are strangers. A child sexual abuse offense where the perpetrator is related to the child, either by blood or marriage, is a form of incest described as intrafamilial child sexual abuse.
The most-often reported form of incest is father-daughter and stepfather-daughter incest, with most of the remaining reports consisting of mother/stepmother-daughter/son incest. Father-son incest is reported less often, however it is not known if the prevalence is less, because it is under-reported by a greater margin. Similarly, some argue that sibling incest may be as common, or more common, than other types of incest: Goldman and Goldman reported that 57% of incest involved siblings; Finkelhor reported that over 90% of nuclear family incest involved siblings; while Cawson et al. show that sibling incest was reported twice as often as incest perpetrated by fathers/stepfathers.
Prevalence of parental child sexual abuse is difficult to assess due to secrecy and privacy; some estimates show 20 million Americans have been victimized by parental incest as children.