And today, the Daily Star reveal what that secret is.
Rob tells Jonny that he's Carla's real, biological dad and then demands £10,000 to keep quiet with the shock news!
The Star says that Johnny confides in Liz McDonald and admits to having a one night stand with Carla's mum. In scenes filmed earlier this month Johnny tells Liz: "It's a relief just to tell someone. She doesn't know, neither do my kids and I don't want it getting back to them because there's no point stirring things up at this stage. I always suspected it but I shoved it to the back of my mind."
Concerned Liz asks: "Why didn't you ask her mum? and Johnny replies: "I told myself it couldn't be, it was just the once and Sharon put herself about a bit, it could have been anyones. Also, I suppose in a way I didn't want to know, I was married at the time. It's not something I am proud of."
Johnny will then go off and attempt to carry out a secret DNA test without Carla knowing what he's up to. Everyone will have to wait and see the outcome of the DNA test and whether or not Johnny pays Rob the money he's demanding.
Now, hang on a cotton-picking-knicker-stitching minute. If Jonny is Carla's real dad, does this mean she married her cousin? Well, yes. It means she married her third cousin Paul Connor. Time to bring out the Connor family tree again!
Deirdre: A Life on Coronation Street - official ITV tribute to a soap icon. Available here.
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