Both of the hatchlings are in the same nest, which is marked C7 on the zoo’s online penguin map and can be seen on the penguin cam .
Another egg has already started to crack and should hatch shortly, with the rest of the eggs hatching over the next few weeks.
Senior penguin keeper Dawn Nicoll said: “We are really happy that the first of the Gentoo penguin eggs have hatched.
“Penguin breeding season is always a really busy time for us, right from the moment we put the nesting rings into the enclosure, through the incubation period, to the hatching, rearing and, eventually, the fledging of the chicks.
“It is always incredibly rewarding when the eggs start hatching and we finally get to see the penguin chicks.
“The majority of them will hatch over the next two to three weeks as the birds will not all lay at exactly the same time. Fingers crossed we will have quite a few chicks keeping us busy this season.”
The breeding season at Penguins Rock began in March, with the “customary squabbles and flipper slaps” as the penguins raced to claim their favoured nest rings and the accompanying pebbles, the zoo said.
The first eggs were laid just in time for Easter – at the beginning of April – and the birds have produced 40 eggs.