Swapping a holiday for a personal matter?

There is a law, the Law on the Right to Leave for Urgent Family Reasons, which gives workers the right to leave from their employment for urgent family reasons related to illness or accident and which make the immediate presence of the worker absolutely necessary.
This law gives you the right to leave, but not paid leave. Some collective agreements provide for paid leave for urgent family reasons, funerals, estate administration, etc. so check if and which collective agreement you are covered by.