The first sign of puberty in boys is increase in testicular size which will start from 10 years on wards normally. The second sign is development of pubic hair. After this stage the penis length and width increases. And the definition of delayed puberty is if first sign of puberty (Testicular size increase) is not there at 14 years. So as your child is now 11 1/2 years you need not worry. you can wait 2 more years for the changes mentioned. Hope your doubts are cleared.