Zookeepers never expected a 23-year-old giant panda to give birth again when she was moved to a nature reserve in southwest China to live out the rest of her days.

But Haizi, started showing interest in courtship this spring, resulting in a blind date with a male panda suitor. Four months later twin cubs, that have made her the world's oldest panda mom, China's Giant Panda Conservation and Research Center announced on Thursday.

A 23-year-old giant panda is equivalent in age to an 80-year-old human.

According to the centre, Haizi gave birth to a 175-gram (6 ounces) female and a 123.1-gram male on July 30 at southwest Sichuan province's Wolong National Nature Reserve, where 21 panda cubs have been born this year. Haizi last delivered a pair of panda twins when she was 19 years old.

“Generally, the maximum breeding age for giant pandas is 20 years old, and pandas older than that are not encouraged to participate in breeding,” Li Desheng, a giant panda expert at the breeding centre, said in a statement.

“But Haizi's success demonstrates the advanced degree of care offered at our centre. It is a breakthrough in panda breeding. “

In Chinese culture, a set of boy-girl twins are called “dragon-phoenix babies.”