TWIN centenarians Cheung Yuet-kiu and Cheung Moon believe their reunion after nearly 90 years must have been arranged by God. In a miraculous turn of events three years ago, the sisters, both devout Christians, found they had been booked into the same home for the elderly. Their parents had arranged for Moon, said to be the younger, to marry into a wealthy family in Guangzhou at the age of about 10. Moon subsequently moved out of the Cheungs' walled farming village in Shap Sz Heung, Sai Kung. The sisters lost contact as it was not customary in traditional Chinese society to maintain close links with married daughters, as they were sometimes regarded simply as having been goods sold. ''Transport was not good in those days and my family was very poor. I had to concentrate on my farm work. Therefore, I was not able to look for her,'' said Yuet-kiu, barely audibly, in her hakka dialect. Yuet-kiu had a son with her husband who also kept a concubine. The son emigrated to Malaysia more than 30 years ago and she does not know what happened to him. Yuet-kiu has been on public assistance since the early 1960s and only until a few years ago had been living in Shap Sz Heung with her husband's daughter by his concubine. Her allowance of $1,800 covers the home's monthly fee of $1,191 and some minor purchases at local fairs. Moon was widowed 20 years ago and her two sons - one of whom was a rural guerilla - were killed in China during the Japanese occupation in World War II. She is being supported by the family of her only granddaughter, who has just emigrated to Britain. Their miracle happened in 1990 when Moon, whose deteriorating health called for better attention, was sent to the Asia Women's League Chan Kwun Tung Care and Attention Home for the Elderly in Kowloon Tong. The home's welfare worker, Chung Wai-kwong, said: ''When we saw Moon's photo in her admission form, we all felt very strange, the way she and Yuet-kiu looked very much alike. At that time, Yuet-kiu had already been in the home for two years.'' They were brought together and stories they told of their lives confirmed they were the long-lost sisters. And if there is any more doubt, one only needs to know that Yuet-kiu means ''as pretty as the Moon''. Moon, now deaf, blind and confined to a wheelchair, did not find the home very comfortable at the beginning. But Yuet-kiu does her best to cheer her up, chatting to her throughout the day. She said that being the elder sister made this her duty. But the pair sometimes argue, especially when they wander into subjects of self-interest. ''Moon likes to babble about her past which is unbeknown to Yuet-kiu. Then Yuet-kiu would say something else,'' Mr Chung said. Moon's memories of her past are confused and her concept of marriage is still childishly old-fashioned - ''Have you been sold?'' she keenly inquires. There is still one crucial piece of information unknown to either sister - their actual age. According to their Hong Kong Government identity cards, Moon is 102, four years older than Yuet-kiu. Mr Chung explained that in the past people often registered a younger age for the sake of securing a better job. The lack of Chinese birth documentation made that possible. Although the twins cannot recall the date or even the year they were born, they are adamant they are at least 100. Yuet-kiu said: ''I'm too old to do any labour, except eating and sleeping.'' The home's workers still get the two old women mixed up sometimes. They solve this by putting a hakka hair band on Yuet-kiu.