Go gently. Don't force it if his young hands are too uncoordinated yet.
I tried once to teach a friend's 5-year-old girl to knit.
But Jenny's hands just plain couldn't handle it... so I instead made Daggone-Sure-Certain that little girl associated knitting with love and warm fuzzies: I took her on my lap, put her hands on my needles, then my hands on hers - and we both knitted together.
Just a square... then a second square to sew together for a potholder for her Daddy.
Hope this helps,
PS - a wee Scottish laddie? Tell him you'll teach him to knit so later he can knit his own ceremonial Scottish Knee Socks to go with his Kilt.
Traditionally, that's why Scotsmen learned to knit - to make their own stockings.