Reuben Blake has just started primary school but he will be 10 before his twin sister is old enough to join him. For although the brother and sister were conceived from the same batch of embryos, they are born five years apart.
Simon Blake and his 38-year-old wife Jody had been trying to start a family without success and began fertility treatment in 2005.
During the medical process, five embryos were created and two implanted in Blake, which resulted in the birth of Reuben on December 9, 2006.
The remaining three embryos were frozen until the couple, from Gloucestershire, London, decided to try for another child last year.
The final embryo was successfully implanted. Simon said, "We got very lucky first time around. We were just overjoyed at having Reuben, he was healthy and happy. But after some time we thought that most of our friends who had conceived naturally had had second child and we wanted to complete the family."
Simon added, "You just can't comprehend that a life could come from some material that's been frozen for that length of time."
Floren arrived on November 16 2011 -- two weeks before her due date -- but five years after her twin brother. Blake said, "When people take an interest in a newborn baby and with Reuben around as well, I find it very difficult to resist the temptation to say 'Oh and by the way they are twins'."
Oldest twins celebrate birthday Two sisters celebrated their 102nd birthday yesterday as officially the oldest twins in the world. Ena Pugh and Lily Millward, who were born on January 4 1910, have always shared their big day with each other.