Thanks to the Mathstart books we've been reading, i am able to introduce fractions to Sonshine boy. We read this and this books about Fractions. Honestly, i don't recommend these books, it's pretty confusing for the child if you ask me. In fact, i've been reading blindly to the kiddo without explaining much. I don't know how much he actually understood!
But what he understand is, that each piece is 1/2 in size when we divide something into 2 equal parts, 1/3 when dividing into 3 equal parts, 1/4 for 4 equal parts etc.
To make it clearer for him, i demonstrated the meaning of Fractions to him by using our Playdough. I rolled a piece into one long strip on a paper and wrote '1' beside it. I rolled another strip and cut it into 2 equal (i tried!) parts. I asked the boy how much was each piece and he could tell me 1/2. And i went on with the demo till we hit 1/4.
I also showed him that when we add all the equal pieces, we get 1 whole piece. I deliberately skipped 1/5 and cut a strip into 6 parts. I asked him how big was each piece and he said 1/6. Yay, he got it!