Well, the problem with that statement is manifold.
Your brother who believes he is God would be blaspheming.
John 10:33
“We are not stoning You for any good work,” said the Jews, “but for blasphemy, because You, who are a man, declare Yourself to be God.”
Hypocrisy is Satan's forte.
He would appear to be your best friend, just like his children.
2 Corinthians 11:14-15
And no wonder, for Satan himself masquerades as an angel of light.
15It is not surprising, then, if his servants masquerade as servants of righteousness. Their end will correspond to their actions.
Luke 12:1
In the meantime, a crowd of many thousands had gathered, so that they were trampling one another. Jesus began to speak first to His disciples: “
Beware of the leaven of the Pharisees,
which is hypocrisy.
Matthew 23:33
You snakes!
You brood of vipers!
How will you escape the sentence of hell?