Because your siblings have CAH we know that your parents are both carriers of CAH. This means that both of them have a normal gene and a CAH gene. You can have all normal genes if you got a normal gene from each of them. You have a 25% chance of this, a 50% chance of being a carrier and a 25% chance of having CAH (which we know you don't) so we can in effect eliminate that percentage. Knowing this info, now you have a 1/3 chance of having all normal genes and 2/3 chance of being a carrier (one normal and one CAH gene). Glad for the good news!!