Back in the 70s and beyond it was not uncommon for multiples to come as a complete surprise in the delivery room and that was exactly what happened for the mum of identical twins Kat Hewson and Viv O'Shea.
"Mum found out she was having twins just after my sister Viv was born, just before I made an appearance," explains Kat, now 46.
"The GP actually told mum after Viv was born that she may be having triplets but it turned out it was just the two of us - that was enough for her."
That was the year before scans were introduced and, as there was no history of twins in the family, 'everyone just thought she was huge'.
"Dad always joked that he was going to build her a platform with wheels on it so she could put her stomach on it. It was also in the days that fathers weren't allowed in the delivery suite so dad was in shock when the doctor congratulated him on his twin girls. His response was 'Umm no, we were just having the one'."
The youngest by five minutes, Kat lived up to her role of younger sibling, according to Viv.
"When we were teenagers Kat tended to get into a bit more trouble than me. I was definitely the more sensible one."
However, they both used their identical looks to pull the odd prank, once swapping classes for the day at intermediate school.
"The teachers didn't have a clue but our class mates all knew there was an imposter amongst them," Kat recalls with a grin.
"A workmate of Viv's recently came up behind me in the supermarket and gave me a big hug. It wasn't until I said: 'Do you know Viv?' that she realised she didn't know me."
"Stuff like that is pretty funny," adds Viv. "I'm used to saying: 'You must know Kat.' The reactions are priceless."
Although they have long dropped their own twin language - speech therapy classes sorted that out - the sisters say they are similar in speech and the way they fling their arms around when they talk. "We sound identical on the phone - mum often has to really listen to pick up on which one she's talking to."
They often meet for lunch and turn up dressed the same and 'that just looks weird!" exclaims Kat. "We feel people looking at us and we are like, 'why are they staring at us?' Then we realise.
Other similarities include both having one son, who, along with older sister Janine, never get the twins mixed up. "They probably know us best."
Both Kat and Viv have a close relationship with Janine, who they say, has always been protective of them.
"I do feel stink at times because Kat and I are so close, sometimes we unintentionally leave her out without meaning to. She's pretty cool though, she usually just rolls her eyes and says something about it being a twin thing," Viv says".
Adds Kat: We live in the same street and I think Janine, who also lives on the same street, gets frustrated with us at times, but the three of us are really close.
"Viv and I have always had the twin connection," continues Kat, who experienced heart burn throughout Viv's pregnancy. We are very alike in some ways and total opposites in others, I'm a graphic designer and she's a crime analyst, We often don't have to explain how each other is feeling, we just instinctively know. Living just a couple of doors down, makes it easy to pop over and make sure everything is ok.
"People often ask what it's like to be a twin, which we can't answer as it's the only way we know. I could never imagine not being a twin."
Adds Viv: "I'm glad I'm a twin, although I don't know any different. Being a twin means you're never without your best friend."