Banquo's royalty

I do not think Banquo is loyal to Duncan. If Banquo is loyal to Duncan, he is supposes to report any unusual movements around the Scottland, but when the three witches predicted that Macbeth is going to be the king, he did not report this to Duncan, after the first two predictions become true, he still did not tell this to Duncan. Instead, he keeps this secret between Macbeth and him. Why does he do that? It is easy to figure out; because the witches also predicted that his children will be king after Macbeth.
If Macbeth really becomes the king, then as his best friend, Banquo can get a good position too. If nothing happens, then he can continue his life as a general of Scottland, another reason is that Banquo’s children are going to be kings, if the witches prediction is correct for Macbeth then the prediction must be true for him. He wants to see his kids to become the king. So that, as their father, he can get alot of benefits.
From these issues, I think Banquo is not loyal to Duncan, since he keep secrets from Duncan which cause his death and did not tell everyone about it is Macbeth who killed Duncan since he knows about it, he does not do what he was suppose to do. That is why I think Banquo is not a loyal servent to Duncan.