What is the role of the Commissioner of Family Law in determining the best interests of the child?

'In the proceeding at bar it is not respondent's (Commissioner's) judgment as to what is for the best interests of the child, but that of the court which is determinative. The custody of an infant may not be controlled by the established practice of an organization no matter how noble its motive may be. Like any other qualified witness, respondent was entitled to present proof before the court, but the responsibility for determining what course would aid the child's welfare is solely and independently the duty of the court in the exercise of its broad powers to deal with the custody of infant children.' (citation omitted) Kurtis v. Ballou, Supra.