Former deputy prime minister Barnaby Joyce and his partner Vikki Campion have welcomed a baby boy, named Sebastian.

Key points: Barnaby Joyce resigned as deputy PM amid pressure over his affair with Vikki Campion and news of her pregnancy

Barnaby Joyce resigned as deputy PM amid pressure over his affair with Vikki Campion and news of her pregnancy It prompted change in ministerial standards to ban sex between ministers and their staffers

It prompted change in ministerial standards to ban sex between ministers and their staffers Baby Sebastian was born at Armidale public hospital on Monday

He was born at Armidale public hospital on Monday this week, weighing 3.8 kilograms.

Mr Joyce quit as Nationals leader and deputy PM in February amid pressure over his relationship with Ms Campion, his former staffer, and the news of her pregnancy.

Mr Joyce almost shares a birthday with Sebastian — he turned 51 on Tuesday, the day after the baby was born.

He has four daughters with his wife Natalie. Sebastian is Ms Campion's first child.

The couple's affair raised questions about whether the statement of ministerial standards was properly followed, when it emerged Ms Campion moved from a media adviser's position in Mr Joyce's office to a job with his Nationals colleague, Matt Canavan.

It also prompted Prime Minister Malcolm Turnbull to ban sex between ministers and their staffers.

Mr Joyce told the ABC earlier this year the end of his marriage was "one of the greatest failures of his life", and his affair had caused incredible pain for everybody involved.

Three weeks after news of the affair broke, he stepped down from his ministerial position, acknowledging the controversy had left him with little choice.

On stepping down he said private citizens like his family needed to be protected from the kind of extreme observation seen in the fall-out of his affair.

"It's incredibly important that there be a circuit-breaker, not just for the Parliament, but more importantly, a circuit-breaker for Vikki, for my unborn child, my daughters and for Nat," he said.

"This has got to stop. It's not fair on them. It's just completely and utterly unwarranted, the sort of observation that's happened."

But last month, Mr Joyce chose to tell the media the paternity of his partner's then-unborn child was a "grey area", adding that he was planning to raise the child as his own regardless of who the father was.

At the time, he pointed out his travel pattern around the period the baby was conceived in June last year.

A day later, he declared the child's paternity "nobody else's business", and reportedly told Fairfax Media on Friday the arrival of the baby had "comprehensively removed any doubts about paternity on the basis of date".