@Steppemum
ds is 15. He showers every day, sometimes twice. He is actually very clean. I have just walked into his room, where he has been all day, and was knocked back by the smell. Not nasty as in unclean/unwashed etc, just teenage boy, it just smells of BODIES.
and @GreatDuckCookery
Have you had a adolescent son?! I have and can tell you that they do need a clean shirt every day.
Have you both taken your sons to the doctors?
Serious question.
My son (now an adult,) never stunk like that. OR my daughter. (Also now an adult.)
Unless they have some kind of skin disease, or infection, or serious issue with B.O, they should not stink in the manner you are describing.
@thewinterofourdiscounttentsmk2
You realise that you are talking to other people though, right? Not just you. Perhaps they have younger children, so insisting they should do what you do based on your circumstances is pretty silly, don't you think?
Hmm, yeah. And defensive too! 
GreatDuckCookery
My point still stands that they need a clean shirt on everyday.
They really don't. Not - as I said before - unless there is something wrong with them (like a skin disease, or chronic B.O.)
I really do suggest a visit to the doctors, for anyone who has a son that is a stinky as you and steppemum describe!