Qualified marriage and family therapists in the Netherlands are licensed by the Nederlandse Vereniging voor Relatie- en Gezinstherapie, the NVRG (Dutch Association for Marriage and Family Therapy).
The association promotes the quality of couple and family therapy, controls the quality of the post-master training for system therapists (marriage and family therapists) and is involved in scientific development of the subject. You can turn to the association to find out if someone is actually qualified and registered as a licensed marriage and family therapist.  

The NVRG has described her vision on marriage and family therapy in her Vision Document.