tl;dr:
No.
Asylum applicants do not need any relatives in The Netherlands. Asylum is granted (or denied) on basis of having the need for asylum for one person.
Family relationships only come into play if relatives of the asylum seeker who do not meet asylum rights status themselves also want to come and live there. In that case one relative is required to be legally in The Netherlands already.
Only if a close core family relationship cannot be proven using official documents comes any DNA testing into play, optionally.
Further applications of other people, including family members, for immigration or permanent residence can be made but are not regulated by asylum laws and regulations.
Something is very wrong with this claim. The Netherlands have one of the strictest laws for asylum in Europe. But the conditions for getting it they list as:
Conditions
You may be granted a residence permit if you meet one of the following conditions:
- In your country of origin, you have real reasons to fear persecution because of your race, religion, nationality, political convictions or because you belong to a particular social group.
- You have real reasons to fear the death penalty or execution, torture or other inhuman or humiliating treatment in your country of origin.
- You have real reasons to fear that you will be a victim of random violence due to an armed conflict in your country of origin.
- Your husband/wife, partner, father, mother or minor child has recently received an asylum residence permit in the Netherlands.
Asylum seeker
Not even
Family member of refugee
You wish to travel to the Netherlands to live with your family member.
mentions anything like having such a large group of relatives already living in the Netherlands.
Since many European countries have relatively easy accessibility for asylum compared to real immigration, claiming asylum is often used and even confused with immigration and naturalisation/integration. Immigration to the Netherlands as non-EU citizen is equally difficult, but nowhere near the requirement of proving 15 family members being already there.
Civic integration examination: condition for residence permit 'humanitarian non-temporary' and 'permanent stay'
If you apply for a permanent residence permit or for a temporary residence permit on non-temporary humanitarian grounds following a 5-year stay with a family member, you must have obtained the civic integration diploma.
Conditions
There are certain conditions that apply to everyone. In addition, you must meet the following conditions for the permanent residence permit:
- You have been living in the Netherlands for 5 years or more with a valid residence permit. Unless you fall under an exempt category. The IND looks at the 5 years immediately before you submitted the application. Only the years from the moment you turned 8 years of age count towards the application for a permanent residence permit. In other words, you cannot get a permanent residence permit until the moment you turn 13 and you have lived in the Netherlands since you were 8 years old with a valid residence permit.
- You have had an uninterrupted 5-year stay in the Netherlands before submitting the application. This means that in those 5 years you have not stayed outside the Netherlands for 6 or more consecutive months, or 3 years in a row for 4 or more consecutive months.
- You have a valid residence permit the moment you submit the application. This has to be a residence permit for a non-temporary purpose.
- You are registered in the Municipal Personal Records Database (BRP) in your place of residence (municipality). You do not have to show this. The IND checks if you meet this condition.
- You have an independent sufficient and sustainable income.
- You have a civic integration diploma. This shows that you read, write, speak and understand sufficient Dutch. In some cases you do not have to take the civic integration examination.
It looks like for all cases — whether personal asylum, family-related asylum, temporary stay, permanent residence, naturalisation — the number of 15 family relatives does not play any role at all.
The actual practice in for the current asylum process in The Netherlands regarding their special regulations, that is non-EU harmonised protection status is detailed from the Alien Act (PDF) and analysed for it effect and practices by the Justitie, Immigratie en Naturalisatiedienst in "The Practises in The Netherlands Concerning the Granting of Non-EU Harmonised Protection Statuses" (PDF)
The provisions laid down are only codified for immediate family members (nuclear family). But the UNHCR emphasises that
Note that no policy has been laid down in Dutch laws and regulations in respect of all other family members, such as grandparents, uncles and aunts. However, all family members of residence permit holders in the Netherlands may submit an application for family reunification by relying on the right to family life, as described in Article 8 ECHR.
There are no specific arrangements in law for people who are resettled in the Netherlands. Every asylum-seeker who meets one of the criteria of article 29 of the Aliens Act can receive a temporary residence permit for asylum. After five years, the holder of a temporary residence permit can apply for a permanent residence permit. If the circumstances in the country of origin and in the personal situation have not changed, a permanent residence permit can be granted. (PDF)
Regarding the use of DNA testing in The Netherlands in matters of asylum or immigration:
Can the families of asylum seekers come to the Netherlands?
Once an asylum seeker has a residence permit, their spouse or registered partner and their children can come to the Netherlands. The right to family life is protected in international agreements about human rights.
Demonstrating a family relationship
Once an asylum seeker has been granted a residence permit they have three months in which to apply for family reunification. Before a partner or family member can join them, documentary evidence of the family relationship must be provided. The Immigration and Naturalisation Service (IND) checks the documents. For more information see the conditions for the admission of family members on the IND website.
DNA testing of family members
If no documentary evidence of a family relationship can be provided, the IND can ask for a DNA test to be carried out. It can also carry out or commission an identification interview to establish that a family relationship exists. This involves interviewing the family member at a embassy or consulate.
That is: one relative of a core family must have legal residence status of any kind in The Netherlands for the others of that group to come… (Excluding extra wives in case of plural marriages or bigamy). The application form in English language (PDF)
There are really only two occasions at all (that I could find) that the magical "number 15" comes up in these documents. Over the age of 15 applicants for permanent residency need to take the integration test. And under "conditions for family reunion"
As of 15 years of age you sign a certificate of non-impediment with your application.
How this could be conflated into the claim is beyond me.