The Prime Minister today led sombre tributes in the Commons after Conservative Party leader David Cameron's disabled son Ivan died early today.
Mr Brown, whose own baby daughter died after just 10 days in 2002, expressed sorrow at the death of six-year-old Ivan.
Wearing a black tie, he gave condolences on behalf of the House to Mr Cameron, his wife, Samantha, and the Cameron family.
"Every child is precious and irreplaceable and the death of a child is an unbearable sorrow that no parent should ever have to endure," he said.
Mr Cameron and Mr Brown would normally have been slugging it out in fierce exchanges - probably over the state of the economy - at this time of the week.
But Prime Minister's question time was suspended after Ivan's death was announced and replaced by brief tributes from each of the parties instead.
The sitting is due to be suspended afterwards, with normal business resumed at 12.30.
As MPs gathered in sombre silence, Mr Brown, after paying a brief tribute to servicemen who had died in Iraq and Afghanistan, said: "I know that the whole House will want to express our sorrow at the sad death this morning of Ivan Cameron at the age of just six years old.
"Our condolences go out to David, to Samantha and the Cameron family.
"I know that in an all too brief life, he brought joy to all those around him and I know also that for all the days of his life, he was surrounded by his family's love.
"Every child is precious and irreplaceable and the death of a child is an unbearable sorrow that no parent should ever have to endure.
"Politics can sometimes divide us. But there is a common human bond that unites us in sympathy and compassion at times of trial and in support for each other at times of grief.
"Sarah and I have sent our condolences to David and Samantha and I know the whole country - our thoughts and our prayers - are with David, Samantha and their family today."
For Tories, William Hague thanked the Prime Minister for his tribute, acknowledging that Mr Brown understood "as much as anyone" the "dimensions of this loss".
Mr Hague, who spoke to Mr Cameron before making his statement, said: "Ivan's six years of life were not easy ones.
"His parents lived with the knowledge for a long time that he could die young but this has made their loss no less heartbreaking."
He added: "Ivan their son suffered much in his short life but he brought joy and love to those around him.
"As David himself has said in the past, for him and Samantha he will always be their beautiful boy."
The Camerons were "hugely grateful" to the NHS care workers who "not only did their utmost for their son this morning but have helped every day since he was born".
Mr Hague said Mr Brown's words had been "very generous and heartfelt".
He added: "I also want to thank the Prime Minister for suggesting that we suspend the normal exchanges at Prime Minister's Questions and the Speaker for agreeing to this exceptional action, which is deeply appreciated by David's friends and colleagues in every part of the House.
"As much as anyone in the House the Prime Minister will understand the dimensions of this loss, something which, as he has said, no parent should have to endure."
Vince Cable, Liberal Democrat deputy leader, said: "Can I just say a few words on behalf of my party leader, my parliamentary colleagues and my party to extend our deepest sympathy to the Cameron family for the loss of their son Ivan this morning.
"I think everybody in the House has experienced bereavement but there is something especially sad and shocking about the loss of a child.
"We recognise, I think all of us, that this is something that is especially difficult to cope with.
"I would simply express the hope that this is a personal tragedy that transcends all party barriers and I would simply want to express the hope that the family are given the space and there is privacy to grieve and cope with this tragedy that they have experienced."
Speaker Michael Martin said: "This House will share with me its sadness at this news and our hearts and sympathies go out to David and Samantha and to Nancy and Arthur.
"As a mark of respect to Ivan this House will suspend until half past twelve o'clock this day."Reuse content