Choose your situation
Your family members live in a country of the EU, of the EEA, in the United Kingdom or in Switzerland
They are entitled to medically necessary care in other EU/EEA countries, Switzerland and the United Kingdom. For example, if they're on holiday there. They do need an EHIC (European Health Insurance Card). You can apply for an EHIC
for your family members online. The EHIC is not valid in their country of residence. There they'll have to use the local health insurance card. To cover healthcare costs during holidays in countries outside the EU/EEA, Switzerland or the United Kingdom, you need to take out extra insurance or travel insurance.
Your family members live in another treaty country
Do your family members not live in an EU/EEA country, Switzerland or the United Kingdom? Then they are not entitled to an EHIC. And also not to reimbursement of necessary medical care or medical treatment in other countries. To cover medical expenses when staying in other countries, you need to take out extra insurance or travel insurance.
Going to another country for medical treatment
Do your family members want to go to another country for medical treatment? Then they first need permission from the healthcare insurance fund in their country of residence. Do you only want to buy them medicines there? Even then, you must first ask for permission. Do you not have that permission (yet) and will your family members be treated? Or do you buy those medicines without permission? Then there is a risk of having to pay the costs yourself.
Read more on I want to go abroad for medical treatment
With your EHIC you are also entitled to medical care in other EU countries. For yourself, apply for an EHIC at your Dutch health insurance company. You also need to ask them if you need permission for treatment abroad.