To proof you are the father and son, you will need to show your ID and your son govt. issued ID which will show the father name of Sancho.
If he is 17 and does not have an ID, any school certificate can show this. You can send this proof to KTChampions or any reputable DT member whom you trust ,if you do not want to disclose it to public.
If you are not willing to show any evidence, no one will believe your case as this is the most common reason which everyone uses when their alts are caught abusing the campaigns.
If your son name is not Sancho and obviously your name is not be.open, then nothing can be proved. Its does not matter if you come live on whatsapp or come live physically.
I am afraid this was the only hope for you and with further five accounts discovered by KTChampions makes your case even more weaker.
Other accounts (Kutkh, Prod, Bonanzabits) also do not belong to me. There is insufficient evidence that I managed them.