Why is my cat a wimp?

My Kitten is wise and fends for himself. He always gets the treats first and is very sneaky, but our 4 year old is very slow and allows the kitten to steal food from him. He can't jump very high. Kitten even jumps up onto the doorand walks along it. Cat has always been kinda slow since he was a baby. I love him dearly but why does he not stickup for himself?