CORONATION Street finally revealed a 40-year-old secret about Debbie Webster, confirming why she’s so protective of younger brother Carl.

During the nail-biting finale to Thursday night’s episode, Debbie – played by Sue Devaney, is seen looking through a box of old family mementos.

She then picks up a picture of her and Carl (Jonathan Howard) before holding it side-by-side to a hospital band from the day of his birth – which confirms Debbie is actually Carl’s mother.

Looking at the ID band, which had both Carl and Debbie’s name on it, the latter’s eyes filled with tears.

Debbie is battling with vascular dementia, meaning that if Carl is to find out who she really is, he’ll be hit with the realisation that quality time with his mum is limited.

Bill was dad to Debbie and her brother Kevin from a previous marriage, later meeting Elaine who was thought to have fallen pregnant and given birth while the family were living away from Weatherfield.

At the time of Carl’s birth, Debbie was 18 years old, with the new revelation leaving fans to wonder who his true father is.

Whilst it’s been a long-kept secret, fans aren’t completely shocked by the revelation after speculating that Debbie could have been Carl’s mum late last year.

In December, viewers were convinced they had worked it out, with one TikTok user sharing their theory to the streaming app.

They wrote: “Someone said in the comments that Debbie turns out to be Carl’s mother and not his sister.

“Prediction, Debbie’s dementia worsens and she comes out casually with it.”

Another fan echoed: “I’m a few weeks behind and the signs are there. Thought this for ages!” said another fan.

While Debbie is wildly defensive of Carl, the same can’t be said for him after he recently set her up, meaning she faces prison for a crime she didn’t commit.

During the show’s dramatic CorrieDale crossover episode, vicar Billy Mayhew sadly lost his life.

Carl was drunk-driving behind the wheel of one of the cars involved, but dragged Debbie into the driver’s seat while he left her and made a run for it.

When questioned by police, a flustered Debbie struggled to make sense of what had happened and was keen not to throw Carl under the bus, meaning she risks prison for the crime.

Now that we know the true reason Debbie is willing to go down for Carl, she might just end up locked up for his crimes.