What it means
A testamentary guardian is the person appointed in a will to have responsibility for a will-maker's minor children if the parents die. The appointment lets you nominate who you trust to make day-to-day and long-term decisions for your children's upbringing. The rules differ by state and territory, and an appointment generally takes effect when there is no surviving parent with parental responsibility. A guardianship appointment can ultimately be reviewed by a court if it is in the child's best interests.
How it's used
In their wills, the couple named the children's aunt as guardian in case they both died while the children were young.