Two gay male penguins have become fathers to a baby chick in Sydney.

Sphen and Magic became a viral sensation after they were given a spare egg from another couple at the Sea Life Sydney aquarium.

The pair proved they were naturals when incubating a dummy egg, which was given to them by staff.

The couple, collectively known as Sphengic, then fostered a real egg from another couple who laid two during the 2018 breeding season.

The aquarium says as Gentoo penguins usually only have enough resources to successfully raise one of their two eggs, the "back-up" chick often dies.

Fostering the biological couple's egg was the best outcome for all penguin couples and the future of their eggs, it adds.

The fostered egg has now hatched, and officials say the foster parents are co-parenting "exceptionally well" to raise their young.

Proud parents Sphen and Magic | Image: Facebook/SEA LIFE Sydney Aquarium

Born on Friday October 19th weighing just 91 grams, the unnamed chick has also waddled into the history books as the attraction's first sub-Antarctic penguin chick since 2016.

Tish Hannan is penguin department supervisor at the Sea Life Sydney Aquarium.

"Baby Sphengic has already stolen our hearts.

"We love watching the proud parents doting and taking turns caring for their baby chick.

"With that said, the first 20 days of a penguin chick's life are the most vulnerable so it is extra important the chick is very happy, healthy and well fed by his parents."

The as yet unnamed penguin chick | Image: Facebook/SEA LIFE Sydney Aquarium

The incubation period for sub-Antarctic Gentoo Penguins lasts approximately 36 days, with the small beak of the chick 'pipping' out of its egg taking up to three days.

The chick will now stay with its dads for the first five to six weeks, where they will feed it up to 10 times a day.

Once it is big enough it will start to lose its baby penguin fluff, start growing its adult feathers and begin swimming lessons.

The gender of the chick is to be determined in two months' time.