难民一般是需要的,因为他们经常没有可靠的身份证明,所以要通过DNA测试来确认血缘关系。其他的家庭团聚一般是不需要的。
下面是芬兰移民局的官方说法,
When you have submitted a residence permit application on the basis of family ties, you and your family members may be subjected to DNA testing. The test is required if documents concerning your biological relationship are unavailable or cannot be considered reliable, or if uncertainty remains over the biological relationship after an oral interview.