I participated in such a study in an STP, years ago. So it had to be under the auspices of Cascade in some way and was probably by a local university. Of course nothing like that is conclusive, though it might be indicative. And AFAIK any urologist who has studied adult cyclists says it's a problem.

As others have said, it's unlikely to be a problem with your boys. I never had any problem until I was fully mature, and I rode a lot as a kid and teenager, on any saddle. In my case, the numbness was always accompanied by discomfort, one might even say pain except that cyclists interpret discomfort as challenge rather than pain. I don't know if everyone with this problem has also experienced discomfort. Also AFAIK infertility, meaning low sperm count or quality, is not the problem. It's simply the inability to achieve an erection.