Dear rtneuville,
Birth records should be 100 years old before they become public. So we're not allowed to look up his birth just yet.
He would appear in the population records, the socalled "gezinskaarten" of Enschede, which are kept at the municipal archive. These records would tell you the birth dates and places of everyone in his family, where they came from, where they lived in Enschede, and where they went to. See
http://www.enschede.nl/home.html for contact information.
In the period 1938-1940, the "gezinskaarten" system was changed into the "persoonskaarten" system, where all people got a personal archive card on which was written where they lived, who their parents, spouse and children were, etc. Because Egidius Wientjes left the Netherlands, his card went to a special institution:
Vestigingsregister van de Afdeling Burgerzaken te Den Haag
Gemeente Den Haag DBZ / Vestigingsregister
Postbus 12620
NL-2500 DL DEN HAAG
the Netherlands
Because it is less than 100 years after he was born, you should include proof that he is deceased; they need a copy of the death certificate.
Good luck, and kind regards,
Lars Roobol
http://www.familyaffairs.nl