"While it might seem strange to members of the public ... you are both providing care for three, soon to be four, children," the judge said.
The defendants spent more than a year on a joint benefit until April 2013, when Blair filed documents with the ministry claiming she had broken up with Nicholson.
Over the following six years she filed a raft of applications, all of which confirmed she was raising her children alone.
In July 2015, in support of an accommodation supplement, Blair submitted a letter purporting to be from a landlord of Kenmure property, confirming she lived there and paid $320 a week rent.
Just four months later she had her third child and it was four years before she admitted to ministry investigators that the document was forged.
If she had provided the tenancy agreement, Blair said, it would have had both hers and Nicholson's name on and they would have been caught out.
Meanwhile, Nicholson was also overpaid benefits to which he was not entitled.
And, in October 2016, he too filed a letter with the ministry, appearing to show he was renting a two-bedroom flat for $220 a week.
Later inquiries established he did not rent the property and the name of the person who allegedly wrote the letter was fictitious.
Although Nicholson only personally received overpayments of $6529, he benefited from the overall total defrauded of $93,828.
Blair initially maintained she was a sole parent, when finally confronted in June 2019 but confessed to the ruse at an interview just days later.
She said Nicholson would disappear for days at a time, could not hold down a job and it was "easier to lie" to the ministry.
Both defence counsel said the ill-gotten funds had contributed to household expenses rather than frittered away on luxuries.
Nicholson's lawyer Sarah Saunderson-Warner said her client had since found work but would likely be back on the benefit under a sentence of home detention.
While the defendant had previous convictions for dishonesty she said they were dated and not as significant as the current case.
Mr McCaskill, for Blair, argued for community detention to be imposed, stressing it was his client's first time in court.
But Judge Callaghan said the crimes — causing loss by deception, using a document and forgery — were simply too severe.
He declined the Otago Daily Times application to photograph the couple and suppressed the reasons why.