What is the religious ruling regarding a child who, at the age of ten, witnessed his mother committing adultery with his paternal uncle multiple times after the death of his father, and what can he do to forget this, now that he is twenty-seven years old?

The son must conceal the actions of his mother and uncle, and not inform anyone of what he saw. This matter should not lead him to disobey his mother, for he owes her righteousness and obedience in what is good. He should know that repentance erases what came before it; so if they repent, it is as if they never committed the sin. If they do not repent, then he should advise them and pray for their repentance and forgiveness, without explicitly mentioning what he saw.