While the marriage lasts, custody is a duty of both parents together. After separation, Article 127 of the Personal Status Law gives custody to the mother first, then the father, then the maternal grandmother, then the paternal grandmother. The court may depart from this order where the child's interest requires it — the child's interest governs every custody question, not the statutory order alone. This order can still be challenged in court where the child's interest requires a change, and assigning the custodian does not remove the other parent's maintenance or visitation rights.