Belgian passport withheld due to non registration with consulate

Hi, our family is South African.  My daughter lives in the UK and is an eu national by descent. My son, her brother did not qualify for his eu nationality as we as his parents did not register him with the Belgian consulate before the age of 6 as we did not know we had to do this. We managed to register our daughter as she was 3 at the time of us finding this out.  My son is the oldest and only granchild of the family who did not qualify for the passport, he is 31.  Is there any hope of of us obtaining his Belgiun passport as we were not informed by the consulate that children needed to be registered with them in order to obtain this passport?

Your assistance is greatly appreciated

I am assuming that one of you is Belgium?

There is information online that may assist you. Type in 'Belgium by passport by descent' and check out the information available.

My ex husband has his Belgian passport as his parents were born there.

Unfortunately,  my ex husband was not born in Belgium, he was born in South Africa.