Our expert says:
Most probably, your brother's wife was guilty of a crime - the presumption would be that she as an adult probably did most of the seducing, and as an adult was primarily responsible for the decisions involved. And so, probably, was the "beloved uncle".
I am wondering how it came about that you "recently discovered" this, and presumably not from your son, or there would be no question of how to "approach your son with this knowledge".
There are of course no rules about how tom deal with such, fortunately, uncommon situations, other than to be frank, calm, and prepared to listen. Yes, the boy / young man needs to know that he need not feel guilty, and that the guilty parties are not what they may have seemed, and deserve punishment. Often a dilemma arises in that even if the perverted adults were to be charged, any court case would require the victim to testify and this could be highly unpleasant for him, though sensible courts can find ways to make this less ugly. If the accused hires a horrible lawyer, though, they could be cruel in cross-examination.
The uncle is indeed deviant, but not necessarily "sick". Of course you are shocked and concerned. It may be possible to obtain free or nearly free counselling / psychotherapy through your neaest medical school / university or college psychology department, and the complexities of the case though unpleasant for you both, may make it more attractive and interesting for therapists in training ( under supervision ) who could get usefully involved in helping.
You mention that your son was 15 at the time, but don't mention his current age. Presumably he is now an adult. He was young enough at the time to make the role of the "adults" criminal, but not to be held criminally responsible himself ( of course, you'd need a legal opinion on this, and again there should be a free law clinic at your nearest university Law School ).
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