The offspring appeared on Boxing Day - the 10th anniversary of the Indian Ocean tsunami that made Phuket a household word and killed more than 200,000 people around the region, claiming 5395 victims in Thailand alone.
Primatologist Petra Osterberg reported on Phuketwan in July that at the centre, 12 baby gibbons have been born in the wild. But twins are unexpected and left to nature, one would probably perish.
The project continues to release gibbons back into the wild, a remarkable achievement when overdevelopment has become a feature of so much of the island.
The gibbons have yet to be named. During Phuket's development as a tourist destination, gibbons were often used by touts in Patong, Phi Phi and at other spots for profit-making photo opportunities and wiped out in the island's wilds.
Here's the project's Facebook report on the big Boxing Day occasion. More stunning photos can be found at
On Friday December 26, Mee gave birth to twins, one boy and one girl, an exceptionally rare occurrence in gibbons and a new challenge for everyone here at GRP.
We are not aware of any documented cases of white-handed gibbons successfully raising twins, either in the wild or in captivity; they're simply not built to handle more than one baby.
It therefore came as no surprise when very quickly we could see Mee was struggling to manage the twins, who were clinging more to each other than they were to their mother.
Despite her best efforts to carry them around, the smaller of the two babies eventually fell from high in the trees, fortunately landing on the soft, springy top of the acclimatisation cage underneath.
Mee quickly came down and picked him up again but neither infant seemed to find the right position on her body and at times she could been seen carrying them in her feet.
After several hours, overwhelmed and exhausted, Mee sadly abandoned them both on the roof of the cage.
GRP staff acted immediately to retrieve the tiny infants and they were brought from the forest to the GRP main office where a make-shift ICU unit was hastily put together.
Although both babies were awake and alert, we were immediately concerned that neither had received any milk during the day and both bad very low body temperatures.
However both babies quickly took some formula and were placed side by side under a lamp to help warm them up.
Two of our experienced volunteers stayed with them throughout the night, feeding them every one and a half hours and ensuring they were warm and dry.
The Gibbon Rehab Project won the Environmental Excellence award in last year's Phuketwan Best of Phuket Awards. The sanctuary is a non-profit venture and can be visited daily.
How to Get To See The Gibbons
Khao Pra Theaw Non-Hunting Area at the Bang Pae Waterfall, Phuket, is about 9 km east from the Heroines Monument. You can visit see some of the gibbons from the viewing platform. The center opens daily 9am to 4.30pm except Thursdays when it opens until 3pm. No entrance fee.