Oh wow. What a piece of sh!t person he is! I am so sorry you are dealing with this, and with your own COUSIN no less!
I don't know that him impregnating someone is unlawful, but its no more adultery than when he was already cheating in your marriage. Does adultery count in divorce in your state? Most it doesn't any more. Just make sure that your attorney gets you the FULL amount of support you are entitled to for your son, and that the custody arrangement has him with your ex as little as possible. Does he hurt your son, or is your son just being a 3 year old and your ex doesn't pay attention?
I don't know that him impregnating someone is unlawful, but its no more adultery than when he was already cheating in your marriage. Does adultery count in divorce in your state? Most it doesn't any more. Just make sure that your attorney gets you the FULL amount of support you are entitled to for your son, and that the custody arrangement has him with your ex as little as possible. Does he hurt your son, or is your son just being a 3 year old and your ex doesn't pay attention?