Dear Fokke Jan Blom,
Thank you for posting your request on History Hub!
The National Archives does not have the present addresses of former service personnel or their survivors on file. Please review NARA’s Locating Veterans and Service Members web pages for some ideas on how to locate the persons you seek. The Federal agency most likely to have such addresses is the Department of Veterans Affairs (VA). The VA can forward a message from you to the veteran, providing the veteran has filed a claim with VA, and they have an address on record. To forward a message, please write your message and place it in an unsealed, stamped envelope. Also include a note to the VA explaining who it is you are trying to reach and add as much identifying information as you have. Place all of this in another envelope addressed to the nearest Veterans Affairs Regional Office (you can find the address at https://www.va.gov/directory/guide/home.asp). If the veteran is in their records, your message to the veteran will be sealed and the envelope addressed to the address they have on file for the veteran. Please note that the veteran may not have informed the VA of a change of address, so they cannot guarantee receipt of your message. If the veteran receives your note, it is then up to the veteran to contact you.
We hope this is helpful.