Thank you for writing us with this important question about blended families. Your husband’s denial of his son’s problem needs to be front and center in your relationship. It’s not okay for you, and you don’t have to live this way. It is clear that his son has problems that are going untreated and diminishing family life.
It is important to know that you must continually standup speaking out that you do not want to live this way. I highly recommend couples counseling so a professional can help you both work toward a resolution. The counselor can help your husband understand that his effort to help his son is alienating his wife and stepdaughter. Getting a professional to help you through these issues is important.
I would also recommend during this time that you find an individual therapist for yourself. It sounds like this has been going on for a while, and that your husband doesn’t understand how devastating this this is for you. You may need to have an individual therapist in your corner as you work through the details of coping during couples therapy. The find help tab at the top of the page will help you locate someone in your area.