The mother of the identical quadruplet boys shaved numbers into their hair to help teachers and classmates tell them apart. Mum Tan Chaoyun, of Shenzen in Chinas Guangdong Province, shaved the six-year- olds heads with the numbers one to four. She took the drastic step before they started elementary school because she was worried the boys would get mixed up. My sons are identical, even to me, said Tan who reckons the only difference between them is the shape of their eyelids. I could only tell the difference between them by having different ankle tags on them before they turned 18 months old. Even now, their father cant tell which one is which. Sometimes he punishes the second one for something the third one has done.