I'm going to ask my husband to miss his sister's wedding
Why do you want your husband to miss the wedding of his sister?
My sister's boyfriend is a jerk.
You should try your best to not control the decision of your husband. If there is a good reason why you do not want him going then let him know.
The reason is because the guy is a jerk.
Let the husband decide to go or not for himself. Regardless of your feelings about the boyfriend, your husband can do what he wants.