This boy

 This boy has two little teeth now and loves to pat-pat-pat on the floor, on my shoulder, on a book...

 but he loves to pat/tap something on something else - a toy on a book or a pan on a box.  It makes him sooo happy.  He giggles and sings along to his rhythm.  

 This boy is also getting more mobile.  He can go from crawling to sitting now.

 And he likes to pull himself up on things.

But you have to be close by - just in case brother comes to make him laugh.  

Then he forgets that he needs to hold on.... 

This boy has definitely worked his way into our hearts!