Who were Hermes brothers?

Hermes, as the son of Zeus, had many half-bothers among them; Ares, Apollo, and Dionysus.
Hermes, through his father Zeus, was the half-brother of Apollo, Dionysus, and Hercules.
Hermes is the son of Zeus and so has many brothers as Zeus had many children.

Some brothers:

Ares

Apollo

Dionysus

Zagreus

Orion

Heracles

Perseus

Minos

Castor

Pollux

Argus

Tantalus

There are probably more!
Not a full brother, but by Zeus he was half brother of Apollo.