I NEED YOUR HELP - LOST UNCLE

I have a lost uncle. My father spoke of a young boy who came to his home when he was about five years old. All he could remember is that a lady came to the door with a young boy and handed this boy off to my grandfather Cornelias Van Wyngaarden and told him that it was his turn to have him. Evidently my grandfather had fathered a son and this boy's mother didn't want the responsibility of trying to take care of a young boy during the war. I'm sure she was very desperate and feared for the boy's life. My father recalls he stayed with his family for a short time and then one day he was gone. I have desperately tried to find more information and hopefully locate this boy. I was able to verify this information with one of my aunts who has passed away. I have one living aunt who also knows about this boy. The problem is my aunt refuses to talk to me about him and at 92 years old she will not tell me anything because she feels it makes her father look bad and will embarass the family. She said she will carry this secret to the grave. I am very saddened by this attitude because there could be another uncle and cousins somewhere that I would love to meet. Not just an uncle and cousins for me and my siblings but another brother that my aunt could have. In my mind, who really cares if there was a baby born out of wedlock, this was a long time ago and in terrible circumstances with World War II. I just want to know if I have an uncle still living. If anyone knows anything about this, PLEASE contact me and tell me what you know.