At first glance, Jasmine and Simon Billington appear to be like any other loving siblings.
But though Jasmine is eight-years-old and Simon only eight-months, they are in fact genetically considered to be twins.
The brother and sister duo were conceived at the same time with sperm that had been frozen.
Their respective embryos were then implanted in their mother Lisa's womb eight years apart.
"They are theoretically twins because they were conceived at the same time - even though I gave birth to them eight years apart," Lisa Billington, a nurse, told The Daily Mail.
"They were identical as newborn babies - both of them had a full head of black hair - but when people look at them now, they can’t believe that they were conceived at the same time, as Jasmine is eight years older than her brother."
Lisa and her husband Nigel Billington turned to IVF after years of failed attempts to conceive naturally.
"We really wanted a family and we were disappointed when the vasectomy reversal didn’t work. I’d tried other methods too - like drinking soya milk and making sure my waist didn’t go beyond 30 inches," she said.
"I tried to have my body in as good a shape as possible to fall pregnant, but nothing was working. I thought I would never be a mum."
Following the birth of a healthy baby Jasmine, the couple decided to wait several years before attempting to conceive another child, The Daily Mail reports.
Of the twenty-four initial embryos the couple had managed to produce, only five had survived being frozen for seven years.
Of those five only two were deemed strong enough to put back into Lisa's womb.
"We only had one remaining chance with our embryos, so we had to keep our fingers crossed and hope for a miracle," she said.
Simon was born 33-weeks later, and only 16-days after older sister Jasmine's eighth birthday.
"We were so surprised that they had been exactly the same weight - and they both had a head of black hair. As babies, they looked like two peas in a pod," dad Nigel mused.