Irish writer Cecelia Ahern, the daughter of former Taoiseach (Irish Prime Minister) Bertie Ahern, thought she was pregnant with twins until recently.

The millionaire mom-to-be was convinced she was expecting twice the baby joy because her sister Georgina and her first cousin Amy both gave birth to twin boys in the past three years.

The “P.S. I Love You” writer and “Samantha Who?” creator said she was having the same symptoms as her twin-bearing family members.

A close friend told Ireland’s Evening Herald: “Everyone was definitely suspicious she was having twins, even Cecelia herself.

"She had terrible morning sickness all the time, morning noon and night, which is sometimes a sign of twins and she couldn't eat at all, just like Georgina when she was pregnant with the boys.”

Turns out ultrasounds show that Ahern is not following in her family’s footsteps, but the expectant mother is just as excited to have her first child with long-term partner David Keoghan around Christmas time.

"They weren't sure at first but then after the second ultrasound they knew it definitely wasn't two babies.

"She doesn't mind, her main priority is that she has a happy and healthy baby.”

Ahern is not only busy with baby preparations, but is promoting her seventh novel, “The Book of Tomorrow,” which was published last week.

In an ironic twist, Cecelia’s novel will face-off with her dad Bertie’s new book, “Bertie Ahern: The Autobiography.”