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.

Scottish Chambers of Commerce (SCC) chief executive Liz Cameron highlighted the need for 11,000 new roles each year in Scotland's digital and IT sector.
She warned that the vacancies could not be filled entirely by British workers.
Ms Cameron also called for a migration system that responded to Scotland's lower population growth rate.
She said Scotland's projected population growth to 2024 was only 3.1%, compared with a projected 7.5% increase for England over the same period.
She warned that could leave the economy growing more slowly and unable to sustain public service levels.
Ms Cameron's comments came as the prime minister prepares to get Brexit negotiations under way.
Theresa May has set a deadline of 31 March for invoking Article 50 of the Lisbon Treaty, getting official talks with the EU started.
In a statement, Ms Cameron said: "It is time to make the case for a new migration system that works for the UK, works for Scotland and, above all, works for business.
"Free movement of people across Europe may have led us to become complacent about the effort that is required to target the talents that our businesses need across all sectors and all parts of the UK.
"We need to plan now for a system that will be focused on sourcing the right talent, wherever in the world that exists, and in the numbers that meet the demands of our economy."
Giving greater control over immigration to Holyrood has been a key demand of Scottish First Minister Nicola Sturgeon in the wake of the Brexit vote.
However in January the home secretary appeared to rule out the possibility of Scotland being handed powers over immigration after the UK leaves the EU.
Amber Rudd said introducing different rules "would complicate the immigration system, harming its integrity" and cause problems for businesses.

Portrait of Caterina, dated to 1657, has been at Penrhyn Castle, Llandegai, Gwynedd, since 1860 before being provisionally sold.
But the UK government withheld the export licence until February.
This was to enable a UK buyer to raise the money to buy the painting.
Auction house Sotheby's has now confirmed that the overseas buyer has withdrawn an application to take the picture out of the country. It may be loaned to a museum or art gallery.
The subject of the portrait, Catrina Hooghsaet, was a wealthy Amsterdam Christian Mennonite who was married but separated from her husband.
In a statement, the Art Fund said the painting was of "supreme national importance" and its future was still "perilously unsafe".
It had started fund raising to buy the picture for the nation.
Art experts say it is one of the Dutch master's finest portraits.
The twin brother of a firefighter says he complained of bullying at work in the weeks before he killed himself.
[NEXT_CONCEPT]
A Scottish business leader has stepped up calls for a migration system that can fill skills gaps after Britain pulls out of the EU.
[NEXT_CONCEPT]
A £35m painting by Rembrandt, which has been in Wales for 150 years, will stay in Britain for the time being after an overseas buyer withdrew an application for an export licence.