I don't think that the truth ever came out about the extent of his activities, who he perpetrated on, his age, and what he did.
The reason I say this, is because I watched the TV special on this with Megyn Kelly and the Duggars. Megyn Kelly allowed the Duggars to "tell their story", and the minimizing, victim blaming, and justifications were epic.
The "story" was that Josh, as a 14 year old, was "curious", and touched his younger sisters while they were sleeping, on top of their blankets. After the girls told their parents this, Josh was sent away to do labor/construction work. He also had to confess his actions to a church member sheriff.
Afterwards, the girls were reminded to be more modest, and "Josh did not have to change any more diapers, because that is not for boys to do...".
That statement, in and of itself, told me, that a whole lot more went on in the house then the parents would admit. And, we can see based on Josh's particular interests, that much more probably occurred.