Two giant panda cubs born just before Christmas are flourishing at their home in a Japanese zoo.When they were born almost four months ago the twin cubs, female Aihin and male Meihin, only weighed 84 grams and 196 grams respectively. Now the pair weigh six kilograms each.Despite looking almost identical, they have quite different characters. Aihin enjoys rushing to her mother Meimei to drink milk wherever possible, while her younger brother Meihin likes to be alone and take naps.The panda twins have become hugely popular with large crowds travelling to see them at the Adventure World Zoo in Wakayama prefecture, 500 kilometres south west of Tokyo."I have seen pandas so many times on television. However real pandas are far cuter than I thought," said 28-year-old Hiroko Motoyama.Seven pandas have been born at the zoo, proving it is one of the very few places in the world that has had consistent success in expanding its population of pandas which are notoriously difficult to breed in captivity.The zoo says the main reason for success in breeding pandas outside of China is the environment in which the animals are reared.Wakayama is known to have clean air, water and an adequate supply of bamboo. Although they also claim that not pampering the pandas too much is crucial."We should not be too nervous about caring for them. For example if it rains, we leave them alone in the outdoor playground rather than making them go inside. That may be one of the keys to our success," said zoo keeper Tatsuko Nakao.She added that as they have seen the zoo's male panda Eimei, father of six out of seven pandas at the zoo, mating with a six-year-old panda in February, another baby could be on the way this summer.© Independent Television News Limited 2007. All rights reserved.