I’m really sorry that you are finding yourself in this situation. First of all, you should make it clear to him that you made a mistake when you gave in to his request to video tape your sister in the first place and that you will never do it again. Your husband is very, very wrong for asking you to do this, especially without her consent. I understand that you and your sister have had issues in the past, but none of this is her fault.
I also realize that you and your husband are both young and that there is a broad variety in what people find sexually arousing, but the fact that he coerced you into doing this in the first place, she did not give her consent, and he continues to harass you for more, makes this all a recipe for disaster.
Be firm when you tell him no. He chose to marry you, not her, and if he loves and respects you he will honor your boundaries. If not, it’s either time for marital therapy or a divorce attorney.
All the best,
Dr. Holly Counts