James Chilvers was a "tragic innocent victim caught between two warring parents", a judge said.
The 23-month-old was stabbed to death by his mother, Magda Lesicka, 33, after she suffered a mental breakdown induced by a relentless campaign of emotional and physical abuse by Ryanair pilot boyfriend Peter Chilvers, the court heard.
Polish national Lesicka, who met Chilvers, 33, when she worked as a flight attendant at the airline, was jailed in July 2018 for 15 years after she pleaded guilty to manslaughter by reason of diminished responsibility.
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Sentencing her at Preston Crown Court, Mr Justice Dove said: "James Chilvers was not yet two years old when he was brutally stabbed to death by you. It was a sustained attack with a knife in which multiple blows were struck while on his bed at home.
"He was a young child who was dearly loved and cherished by those around him. He was caught as a tragic innocent victim between two warring parents. Whatever the rights and wrongs of that dispute, the last thing that should have happened is he lose his life - killed by a parent."
James's grandparents, retired teachers Richard and Hilary Chilvers, attended the hearing and Mrs Chilvers tearfully read her victim personal statement from the witness box across from Lesicka, who was sitting in the dock.
Mrs Chilvers said: "Because of this tragedy James has been denied the rest of his life. Even at his tender age this was a life full of potential and promise.
"He was just starting to speak and was making rapid progress. On the morning of the day he was killed he recognised the spelling of his name and James said it aloud to us.
"We have all been deprived of James's presence in our life. He was adorable, beautiful, inquisitive and loving.
"We feel let down. For nearly seven years we welcomed Magdalena Lesicka into our family and got to know her well. We gave her kindness, friendship, support and love.
"James's death has devastated our family. We will never again be able to live life to the full."
Peter Chilvers, who denied Lesicka's allegations, was also in court for the sentencing.
In his statement read to the court, he said: "James Andrew Chilvers was a delightful little boy, always cheerful and great fun to be with. I devoted all of my spare time to be with him. He was my life.
"He was exceptionally bright and talented in everything he did. He was beautiful with his blond hair, blue eyes and angelic smile.
"As James's parents we both had great plans and wanted the best for him as James's life had been one great holiday. Due to our lifestyle, James had been used to travelling extensively, visited nine countries.
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"Shortly before his untimely death we purchased a new home that would have provided the stability he needed. He would have had a fantastic childhood and life thereafter. He was so cruelly and viciously robbed of his life.
"Losing James has left a massive void in our life. The experience of the past year has completely broken me.
"The sense of pain, loss and betrayal are far beyond what anyone should experience in their life."
At his trial at Manchester Crown Court in October, Chilvers, from Northwich, Cheshire, admitted he had cheated on Lesicka, from Wythenshawe, since 2014 with another Ryanair cabin crew member.
He said Lisa Spencer was now his current partner and mother to their two girls, aged 16 months and three months.
He told jurors: "She is a very special lady. She has been my rock since everything happened. She has really stood by me. I don't think I would be here now if it was not for her."