I've never learned it. It feels strange, I wouldn't say uncomfortable, but really can't say what exactly. Just strange somehow. Don't force him.
But try to explain to him, that people normally do it (eg like shaking hands). Try to teach him the rules (And find out, that you most likely don't know yourself, how to put it it words, but there are some "tutorials" online about that). Make a game of it once in a while, maybe that would help.
It's definitely a disadvantage in later life, since some people have strange ideas about people not using eye contact (not hones, not telling the truth, shy...) and it's the main key to flirting!
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Deep into that darkness peering, long I stood there wondering, fearing,
Doubting, dreaming dreams no mortal ever dared to dream before (E.A.Poe)