Parental Rights
An order of custody following a divorce does not, in itself, terminate a non-custodial spouse's parental rights. However, courts can hold separate proceedings to terminate parental rights for things such as child abuse or neglect. In such cases, if a custodial parent leaves a will naming someone other than the ex-spouse as guardian, the court will likely honor the appointment.
Parental Abandonment
If a former spouse outlives a custodial parent, she may lose her rights as a minor child's caretaker if she abandons her child. A guardian appointed by the surviving parent is generally recognized in such circumstances. No formal termination of parental rights proceedings are usually required. The act of abandonment is usually enough to allow a non-parental guardianship.
Last Will Controls
Courts always consider a spouse's will for purposes of guardianship appointment. Therefore, all parents should consider making wills and name a guardian therein. For example, suppose Mary, who has custody of her three-year-old son Jake, names her sister, Jane, as guardian of Jake in her will. At the time of Mary's death, her ex-husband, Bob, can step up and provide a good home for Jake. But if Bob should also die while Jake is a minor and doesn't leave a will appointing a guardian, the court may then look back to Mary's will and give preference to Mary's sister, Jane, as guardian.
State Involvement
If an ex-spouse is unable to care for a child and no will exists appointing a guardian, the state steps in after the death of a parent. Volunteering family members are preferentially considered as guardians as long as they are fit to provide care. Otherwise, state foster care programs and court-appointed guardians or adopting parents will tend to the child's needs.