What would you tell your kid if he asked you this ?

My son is 13 and he is my only child however he has 6 half brothers and sisters on his bio dads side ..He doesn't see them hardly ever ..anyhow my sons sister got arrested and it was in the newspaper and my son saw it and said to me " I wonder how long I got b-4 I have to go to jail " I said what do you mean !He said they arrested my sister and I am wondering how long I got b-4 I have to go ... My son has never ever been in any trouble he is a A student and some how he has it stuck in his head that it is hereditary and that it is just in his dna . I didn't know what to tell him ? I told him that although they are related by blood doesn't mean that he will be like his brothers and sisters .. They never really had a loving home and my son has been raised away from that lifestyle .