Karen Rodger, 41, and her husband, Colin, 44, welcomed two girls after a Caesarean delivery. The babies are not identical and are named Isla and Rowan.
The couple already has four boys: Lewis and Kyle, 14, and Finn and Jude, 12.
Doctors told Karen Rodger, 41, and her husband, Colin, 44, that they had a 500,000 to one chance that her third pregnancy would again be twins, The Mirror reported.
"I just could not believe it. It never crossed my mind that it would be twins again, I just thought that just doesn't happen to people like me but I'm absolutely delighted," Karen said.
Karen said she found out the babies were twins during a six-week scan. She texted her husband with the news.
"He thought I was joking and immediately wrote back to say 'this is not funny' I had to explain that it really was true," she said.