Michael Douglas leaves fans confused with ‘weird’ nickname for wife Catherine Zeta-Jones

Some People were left with raised eyebrows after finding out the nickname Michael Douglas has for his wife.

Nicknames can be pretty cute and sweet in any relationship, but this celebrity couple surprised quite a few people when they revealed one of theirs - because they share this one thing in common.

Actor and actress Michael Douglas and Catherine Zeta-Jones share a birthday on September 25, something many fans weren’t aware of.

But while this isn’t anything too crazy, it was how Douglas referred to his wife of almost 25 years that caused a bit of a stir.

Sharing a picture of the pair of them for the occasion on Instagram, Douglas wrote a message to his wife in the caption.

The nickname confused some people (catherinezetajones/Instagram)

It read: “To my birthday sister—what a joy celebrating another year with you! Congratulations on your spectacular game at the Celebrity Ryder Cup. Happy Birthday to the love of my life @catherinezetajones.”

While many fans were complimenting the pair and congratulating them on their birthday, some picked up on the ‘birthday sister’ comment and argued it came across as ‘weird’ to them.

One user wrote: “Did you just call your wife sister or am I tripping?"

Another added: “That’s his wife, not his sister, what does he mean birthday sister.”

In the comments section, Zeta-Jones thanked her husband but didn’t reveal any potential nicknames she has for him.

She wrote: “Happy birthday darling. I can't think of anyone else to share a birthday with.”

On her own social media page, she posted a tribute to their relationship and shared old photos of them through the years.

She wrote in her caption: “Happy birthday Michael! Sharing this special day with you is once in a lifetime!”

Zeta-Jones shared pictures of her and her husband over the years on her page (catherinezetajones/Instagram)

Other fans seemed less phased by the birthday sister comment and focused on the sweet pictures the pair shared of each other.

One fan wrote: “Happy Birthday to my favorite Hollywood couple! My wish for you is to be happy, healthy and blessed! 🥂 To many more Birthday's together! LOVE CONQUERS ALL!"

Another added: “Hoppy Birdy Catherine & Michael wishes for fantastic health & happiness full of love always.”

While a third added: “Happy birthday to you two!! Much health, happiness and many years of life for you and enjoy this very special day.”

With another simply adding: “Happy Birthday, both of you, beautiful couple!”