Just keep reading to him and talking with him and interest in letters will come. If you read to him, and if the reading is a warm and pleasant occasion, he will invariably reach a stage where he asks, “What is that?” as he points to a particular letter or word.
Also, praise him for his math skills. That is more unusual, and perhaps even more to be appreciated and encouraged than early skill with letters and words. Make certain you don’t compare your oldest to his younger brothers with remarks like, “Your little brothers know their ABCs. Why can’t you learn them?”
Make a biweekly trip to the library a special family event and let him choose the books he wants. And limit his TV viewing. The more he watches TV, the less desirous he will be of learning to read.
Our parenting advice is given as suggestions only. We recommend you also consult your healthcare provider, and urge you to contact them immediately if your question is urgent or about a medical condition.