No listening to simple commands

[apples and bananas]

I have 2 children at the 18 month mark. Child A is a good listener, she follows basic commands like "stop" "clean up" "come over here" "please put that down" etc. Child B follows nothing. He doesn't stop (or run faster) when I call him. When we start to clean up, he sees that as time to take things out of the toy bins, I'm seeing no basic listening commands at all. He's a great child though. Very calm, very loving, not aggressive at all.

The other thing that concerns me is that when I come down to his level to speak to him he can't look me in the eye for any length of time. His eyes dart all over the place.

i'm wondering if there might be something there that's concerning... or maybe he's just a late bloomer. There is the whole boy/girl difference too.

Anyone else have the same issues?