Confused? Read on.
Both Lexi and Rudridh Dalgleish were conceived at the same time and were born on December 27.
But their mother Hazel gave birth to them exactly two years apart - after the embryo that became Rudridh was frozen by fertility experts for two years.
The twins were conceived during the same cycle of IVF treatment and Hazel fell pregnant with Lexi, now three, whilst the remaining embryos were frozen for further use.
Daughter Lexi was born on December 27th 2007, and then a year later Hazel fell pregnant again with one of the frozen embryos.
Amazingly, against all the odds, son Rudridh was born on exactly the same date - 27th December - in 2009.
Just to add to the unbelievable coincidence, the twins also share their birthday with their grandmother Joyce, 57.
Hazel, 29, who is married to husband Barry, 45, a crane operator, says: "It really is amazing and we can't believe that although our twins share a birthday - they have been born exactly two years apart.
"For them to be born on the same date, but two years apart, really is remarkable. When the midwives handed Rudridh to me, they were speechless as they all knew that he had been born on Lexi's birthday.
"And the fact that they share my mum's birthday too is the icing on the cake - for three people in one family to share a birthday is unbelievable."
The couple, who live in Sanquhar, near Dumfries, sought help from fertility experts in 2009 after they discovered they were unable to have a family.
Their first cycle of IVF was successful and Hazel fell pregnant. Her pregnancy went smoothly until she was 27 weeks pregnant and her waters broke.
Hazel, an administration assistant, says: "We were beside ourselves with worry. "The pregnancy had gone so well up until then, then all of a sudden our baby's life was in danger.
"The doctors told us that the baby stood a better chance of survival if she was delivered as all the amniotic fluid had gone from my womb."
Hazel had an emergency caesarean at Dumfries and Galloway Hospital and tiny Lexi was delivered, weighing just 2lb 3oz.
Hazel says: "We were so frightened we were going to lose her. We went to see her in the special care unit when she had been born and she was so tiny lying there, she looked just like a tiny baby bird."
But tiny Lexi battled through. She remained in intensive care for two weeks then was transferred to her local hospital for a further six weeks, before finally being allowed home.
Hazel says: "She did so well, she was a real little fighter, and she just got stronger each day.
She had several blood transfusions to help her pull through, but apart from that she didn't need any further treatment. We were so proud of her."
The couple decided they wanted to try for a second baby and in May 2009 fertility experts implanted a further two embryos into her womb.
Again the treatment was successful and her pregnancy went smoothly. The baby was due in January 2010, but he made his surprise entrance into the world when Hazel's waters broke three weeks early.
She says: "We just couldn't believe it when my waters broke. It was Lexi's birthday and we realised then that Rudridh was going to be born on exactly the same day."
Hazel was taken to the Princess Royal Hospital in Glasgow where she gave birth to her son, who weighed a healthy 7lb 2oz.
It was so emotional when Rudridh was handed to me and it was Lexi's birthday as well. The midwives knew that it was Lexi's birthday too and they were amazed that they had just delivered her twin brother exactly two years later, on the same date.
"My mum was very emotional too, as both the children now share a birthday with her."
People do think they are both twins - although they can't believe it when Hazel reveals they were born two years apart.
She says: "They both have blond hair and blue eyes and Rudridh is catching up with his sister in height too - so strangers do think they are twins. When I tell them their birthdays are two years apart, no one can quite believe it.
"It is definitely easier to celebrate their birthdays on the same date. There is a very strong bond between them - it was as if Rudridh was determined to arrive on exactly the same date as his twin sister.
"When they are old enough to understand I will tell them about their remarkable births."
Happy birthday, Lexi and Rudridh!