No. He doesn't understand the concept of invisible things having size. Microwave an ant, it will be fine because the entire ant is smaller than the waves the microwave uses to cook your food. Wifi is multiple orders of magnitude too big to get inside your body and cause harm. Same for any other radio transmission used for data like cell phones.

Any effect would be felt as warmth and at legal wifi energy levels the warmth from the processor is far stronger. The physical warmth from the processor might reduce fertility but the effects are temporary. Like the old advice to switch to boxers if you are having trouble getting the missus pregnant.