Meet the frozen sperm siblings born 15 years after their father was left infertile from cancer

As a family photograph, it is hardly out of the ordinary - two-year-old Mariella hugs her baby brother Herbie.

Yet for parents Ian and Alison Morris, it is a reminder that these are the children they never thought they could have.

Mariella and seven-month-old Herbie were born using Mr Morris's frozen sperm, stored for an astonishing 13 years after cancer treatment left him infertile.

Following his successful battle against the disease, the couple had several unsuccessful attempts at starting a family using IVF and were close to giving up in despair.

But one final try, in February 2007, worked and Mariella was born the following October.

Incredibly, the couple then had a second success last year with Herbie, by which time Mr Morris's sperm had been frozen for 15 years.

Mrs Morris, 37, said: 'I thought I'd never be a mum so to have our two miracle frozen babies really is the most wonderful thing.'

Mr Morris, 49, a design engineer, was diagnosed with chronic myeloid leukaemia in March 1994, three years after the couple married.

His wife, a buyer for a television shopping channel, said: 'We were just so shocked. The level of cancer in cells in his body was so high that the doctors said they were amazed he was still standing.'

Fortunately, Mr Morris's brother Barry was the perfect match for a life-saving bone marrow transplant.

Before the treatment, which involved chemotherapy, doctors warned him to have his sperm frozen as he would be left infertile.

After Mr Morris's recovery, the couple, of Grantham, Lincolnshire, decided to try for a family in 2002.

Mrs Morris said: 'We had been really hopeful when we had our first try at IVF as we knew there was nothing wrong with me, and we were using the frozen sperm. So when it didn't work we were devastated.'

A second and third attempt failed before they went to specialist clinic Care Fertility in Nottingham for a last try.

Mrs Morris said: 'We only had two embryos of good enough quality so we knew we didn't have much of a chance. So when I did a pregnancy test and saw the positive blue line, I just couldn't believe my eyes.

'I went for a scan at six weeks... when I saw the tiny heartbeat on the screen I just burst into tears.'

The record for a live birth from frozen sperm is 21 years, in Manchester in 2002.