Normally, both parents are jointly responsible for the care of their children under 18, unless a court order changes parental responsibility. This means that if one parent dies, the surviving parent would assume sole responsibility for the child(ren). There is no need for any direction in the will.
Where a court makes a parenting order, it stays in force until the court changes it, or the child or guardian(s) dies.
A parent with sole responsibility for the long term care, welfare and development of a child (because of a Family Court order, or because the other parent is not named on the birth certificate, or has died) can state in their will who will care for their minor children after their death.
Whether or not there is a direction in the will, if the carer parent dies and the family cannot agree about who should care for the child, an application to the Family Law Courts may be necessary to determine who should care for the child. For more information, see Arrangements for children.