Joseph Keighley, 42, was a full-time firefighter with Essex Fire and Rescue Service and based in Basildon.
An independent fire service report found no evidence bullying contributed to his death in July.
His twin Jeffrey said Joseph had told him he was being bullied. An inquest in Chelmsford recorded a verdict of suicide.
The inquest heard Joseph Keighley had left a note in which he said: "I am sorry to all but I can't carry on in this life.  It's too hard, too tough."
A wider investigation into an alleged 'intimidatory culture' at Essex Fire and Rescue is under way.
The twin brother of a firefighter says he complained of bullying at work in the weeks before he killed himself.