That is not typical!

Welcome to the forum.

DW and I were the same way until we took Mr W at 4 mos to a company picnic and met other kids twice his age. Our babysitter, who had taken care of lots of kids, had told us all this, but we kind of blew her off. Our pediatrician made the same comments later on.

The book Grinity mentioned is good. But be prepared. Its one thing to intellectually understand, its another to have facts stun you along the way.