Does the Groningen Protocol require parental consent?
First of all, it must be understood that the protocol is essentially illegal under Dutch law in that the Netherlands' "Euthanasia and Assisted Suicide Bill" does not even apply to children under the age of 12. (The link was taken directly from the Netherlands Ministry of Justice website). It may be illuminating, though legally irrelevent, to note that for consenting children between the age of 12 and 16, parental consent is required. For children aged 16 or 17, parental "involvement" is required under the law.
As to whether the protocol itself permits euthanasia absent parental consent, I can only quote the New England Journal of Medicine article where Dr. Verhagen and Dr. Pieter Sauer outline the protocol:
"We are convinced that life-ending measures can be acceptable in these cases under very strict conditions: the parents must agree fully (my emphasis), on the basis of a thorough explanation of the condition and prognosis; a team of physicians, including at least one who is not directly involved in the care of the patient, must agree; and the condition and prognosis must be very well defined."Whether or not this guideline is adhered to is another question but I think this at least clarifies what the protocol states.