The functioning “male part” that enables copulation is attached to the pubic bone. If that’s gone, so is sexual functioning. As far as fathering children with medical assistance, I suppose one intact testicle and a functioning prostate would suffice, and it would be possible to extract sperm from that one testicle in the absence of a prostate, painful as that prospect might be to us males. They’ve done it with the very recently deceased.
I never attended any classes, but had patients that did..