if this guy really wants to try... don't discourage him.

Plenty of kids had their desire to sing or express themselves squashed like a bug by the adults in their lives... so you don't know what his "problem" is.

I used to be a riding instructor - among many other things- and spent quite a few lessons on one adult pupil who never progressed beyond sitting like a sack of potatoes in the saddle. I finally told him that I couldn't keep taking his money if he didn't at least make some effort to learn... and it still bugs me 35 years later.

Bob... I assume you sing & play, which is why he has asked you for instruction. have him hum along to your playing... he needs to make some noise and get the feel for timing & phrasing. If he can do that, then he can move on to lyrics. If not, well at you both tried.