Kristina Davies, 20, and Ricky Winter, 23, had previously denied eight counts of child neglect but were found guilty following a trial at Canterbury Crown Court last month.
The injuries to the boys, who were four and two and cannot be named for legal reasons, included bites to their genitals.
Davies and Winter, from Margate, Kent, also forced the children to stand in a corner with their hands on their heads for long periods of time and screamed in their faces on numerous occasions when they were looking after them in July last year.
During the period the boys suffered an array of injuries including fractured bones, bruises and bites. Their horrendous ordeal took place when they were staying for a ten-day period at the home of Davies and her boyfriend Winter in July 2009.
The boys were staying with them temporarily by arrangement but the nature of their relationship to Davies and Winter cannot be reported for legal reasons.
Some jurors were visibly distressed when they were shown dozens of graphic photographs of the terrible injuries the couple inflicted upon the two boys.
Winter was described in court as a 'violent bully' and his girlfriend Davies was accused of 'sitting by and doing nothing' during the children's nightmare ordeal.
Neither of them made any attempt to call for medical assistance, the court was told.
Witnesses said they saw the boys being attacked by Davies, including when she hit one with a half-full Coca-Cola bottle.
Concerned neighbours called police last summer.
In their defence, the unemployed couple claimed the boys' injuries were caused by them playfully fighting each other and also blamed some of the marks on sunburn.
But Judge James told Davies and Winter: 'The injuries you caused were truly horrific and sickening. This was a systematic and calculated period of bullying.'
Detective Sergeant Paul Deslandes of Kent Police, who investigated the abuse, said afterwards: 'The injuries these children suffered were absolutely horrific. They were the worst officers had seen in my unit and the paediatrician involved in the case said it was the worst case of child neglect they had ever encountered in 30 years of practice.'
Head of the NSPCC Helpline John Cameron said: 'These defenceless young children have suffered terrible neglect at the hands of those who were meant to care for them. Though many people do call us to report children being neglected, there are others who don't act on their suspicions. Young children can't get help for themselves. You could be their only hope. We would urge anyone who has concerns about a child to act on their behalf and contact the NSPCC Helpline.'
• The NSPCC Helpline has run for 20 years, currently receives five thousand calls a month and has helped well over half a million children to date.
• Anyone can contact the NSPCC Helpline service free and anonymously on 0808 800 5000 or email firstname.lastname@example.org, 365 days a year, 24/7, to report any worries or concerns about a child being badly treated.
• The Helpline can give advice on what action callers could take to help a child in future, such as warning signs to look out for and how to get support for their parents or carers.
• If callers provide identifying information about a child and the NSPCC believes that child is at risk, the Helpline advisor will work with the police or children's services to ensure that child is protected.