I heard an acquaintance who was an incest victim at 6 put it this way: "Once you discover sex it's the only game you want to play."
That is such a telling statement. The word 'game' shows how no kid could consent. They've got no idea how one of their actions would effect next week, much less a year or fifty years from then. They don't understand the long-term nature of the things that they're doing (cannot cannot cannot!)
But when we're children, we don't know what we don't know. So it seems like we were all right with it. It wasn't true, but the memories themselves don't hold the information we need to see the lie. Memories hold pain/pleasure, shame/acceptance, and all the lies of manipulation and grooming without a strong counter, or we wouldn't have gone along in the first place.
That isn't to blame victims, just like we would never expect a 5 year old to bench press 200 lbs.
I really like how some of the guys have put it, it's when we sort of link what we understand about sex as adults to the easy-to-see limits of children to really see the difference. It's a big step towards "not my fault."
So, I have hope for your husband and your family. But I'm so glad you're aware and watching. That's so key! Good on you!
We are not defined by our faults, or our wounds, but by the truth within us, which nothing can take away.