His brothers were not believers like His disciples.
They had seen the miracles and had figured that
He could be the Messiah. But their idea of the
Messiah was similar to that of the multitudes.

" For there is no man that doeth any thing in
secret, and he himself seeketh to be known
openly. If thou do these things, shew thyself to
the world.
For neither did his brethren believe in him."
John 7:4-5

They thought if Jesus was who He claimed He
was then why wasn't he telling the whole world.