It's not going to be easy for you, but you are going to have to find your inner child. I learned to just let go and to just play with my nephew when he was a toddler. Turns out it was good practice for when my daughter was born. Look for activities that interest him and try to actively participate in them with him. My nephew loved balls, so I got him a soccer ball and let him kick it at me for hours at a time. Boring, I know, but we have a really great relationship now and he's turning 19 this year. The monotonous repetition when he was a toddler has paid of big time, now that he is becoming a very mature young adult.