Normal
It's highly likely he inherited a mental disorder from one or other or both parents. This is set in stone so cannot be changed. What you and many other parents of these dysfunctional children must do to save your sanity is learn about Anti Social Personality Disorder/ Psychopathy. It is the hardest thing in this world to accept that someone you love and have invested so heavily in has in fact been born without a conscience but it happens. (it affects 1:25 of the population). I'll recommend a facebook page called Psychopathfree and also read The Sociopath Next Door by DR Martha Stout.. I will guarantee that by this time next year you will be an expert on this inherited disorder and will save yourself so much grief ..Take care.