Jordan and Abigail Burling slept in the same room where the dead body of their brother lay hidden inside a wardrobe.
-> Leeds mum, gran and sister condemned Jordan Burling to a lingering death
The trial judge, Mr Justice Spencer, said there was no evidence to contradict Dawn Cranston's account that she secretly put her stillborn baby into a rucksack and concealed it from her family for 14 years.
He told her: "All the prosecution can say is that...in the rucksack were the remains of a full-term baby.
"You say it was a boy. It was not possible to say whether the child had been born dead or alive.
"Only the bones and the teeth remained in tact, from which experts were able to confirm that the child was aged 38-40 weeks."
-> Three generations of same family jailed over teenager left to rot to death at house in Leeds
The mother told jurors at the trial that she intended to bury the body but never got around to it.
The judge said: "All this would be totally inexplicable callous behavior were it not for the fact that....you were suffering even then from this same dissociative disorder, which caused you to be detached from the reality of your behavior.
The judge added: "The strangeness of your behaviour is further demonstrated by the fact that the bag containing your dead child remained in that wardrobe for the next 14 years, throughout much of which period your two children slept in the room only feet away from the decaying body of their dead brother."
The judge described how the family home "was not a deprived household".
Jordan's severely malnourished body was discovered in the next room to where three refrigerators were "well stocked with food."
He said: "It is important to emphasise that this was not a deprived household in material terms, nor were any of you inadequate to the point that you were unable to live a reasonably normal life outside the home.
-> Jordan Burling's relatives 'feel betrayed' by the people trusted to care for him
"Although the house was full of clutter you all had mobile phones, laptop or tablet computers and a great deal of other equipment.
"You Dawn Cranston were the breadwinner, holding down a job at Poundland in Leeds city centre, which involved long hours.
"You Denise Cranston, spent most of your time at home but you were a spritely 68-year-old when Jordan died, well in tune with events in the outside world and very much the mistress of the household.
"You Abigail Burling had a tenancy of a house of your own but you...were at the family home every day and frequently stayed overnight.
"You led a seemingly aimless life, but you were well informed in the matters which interested you, principally sport and cars, which you shared with Jordan."