The laws in most states have not kept up with the reality of divorce and remarriage.
Most states have retained the concept of people only marrying once and do not reflect the reality of the fact that many Americans divorce and remarry, according to The Wills, Trusts & Estates Prof Blog in "Estate Planning for your Step-Family."
In most states, the spouse will get everything, but the spouse will be under no legal obligation to pass anything on to his or her step-children.
When attempting to deal with step-families, it is vital that you have some sort of formal estate plan. At a minimum you need a will. Even better would be a more elaborate estate plan that specifically includes the names of everyone you consider to be in your family and precisely what you want them to inherit.
It should also include those people you do not consider a member of your family, such as former step-children.
An estate planning attorney can guide you through the process of planning for your own unique circumstances including a blended family.
Reference: Wills, Trusts & Estates Prof Blog (Oct. 7, 2016) "Estate Planning for your Step-Family."