As-salamu alaykum,

Children grow and develop at different rates. It could be that your older son will have a developmental growth spurt later on, or it could be that he has a more introverted personality. While you may think he is not attentive, learning or understanding, he may be absorbing the information, but not outwardly showing it for whatever reason.

You did not mention whether or not this is a new phenomenon or you have had him evaluated by a pediatrician regarding your concerns. If you have not yet done so, I would kindly recommend taking him to his pediatrician for an evaluation. Write down a list of all your concerns and be ready to discuss them with the doctor. While it may be that your older son is just developing at a different rate and will catch up, or is withdrawn and more introverted, it is best to rule out any other factor that may be impeding his growth and development. Please do consult with his pediatrician insha’Allah. You are in our prayers, please let us know how he is doing.