The Spouse In Law

In blended families often the most tense relationship exists with your new spouse’s ex. Inheriting a hostile husband in law or wife in law can undermine and disrupt all efforts to make a new relationship work. Worse, this person may use you as the whipping post for all their anger over the divorce and make it difficult to establish the new family. Step children maintain a strong loyalty to the biological parent.
You must establish a new order in a blended family and it falls on the partner to deal with their ex to avoid undermining parenting. Children need a safe and structured environment to grow and their natural distrust of a step parent can be magnified by an angry ex. Your bond with your new partner can be threatened.
Again, each person is responsible for dealing with their ex to neutralize their impact on the newly formed blended family. Once this is done, put on your game face and accept this person. In blended families, this is a lifetime relationship.