Tragic Elon Ellis-Joynes was just 12 days old when he was savaged by cross-breed Alsatian Chow Chow Teddy at the family home in Welfare Road, Woodlands.
The tot suffered 40 puncture wounds during the horror attack, which happened when his mum Abigail Ellis, 28, nipped to the toilet.
Her partner Stephen Joynes, 36, was charged with owning a dog which caused death when dangerously out of control after the horror on September 13 2020 and was jailed for four years after appearing at Sheffield Crown Court.
Judge Jeremy Richardson QC heard Joynes moved in with "vulnerable" mum-of-three Ms Ellis following the death of her previous partner, who she had nursed through illness.
Barristers said Ms Ellis will remain with Joynes in spite of the horror - and the pair "support" each other.
The court heard Teddy was initially a gift from Joynes' ex to their daughter in January 2019. However, Joynes took the pet when it soon became obvious that the mum and daughter "could not cope".
But the animal failed to settle in its new home and on September 13, 2020 carried out the deadly attack after escaping from its pen and mauling Elon who was unattended inside the house.
He was rushed to hospital, but despite the efforts of doctors, died hours later.
Edward Moss, mitigating for Joynes, called the incident "a tragedy by the very definition of the word".
"This is a man who has suffered the greatest loss of all at his own hands," he said.
It was a tragedy waiting to happen... you should never have kept this dog
The couple are still together, but have lost custody of their other children, he said.
"They support each other. They are still together. Their plan is they will get their children back and put this matter behind them," Mr Moss said.
"It's something that he will never forgive himself for."
The dog was destroyed shortly after the tragedy.