Emmerdale's Caleb Miligan will make his arrival this Christmas, leading to huge scenes as the Dingles learn of their long-lost relative.
The secret brother of Cain Dingle and Chas Dingle debuts on Christmas Day, much to the annoyance of Cain who has hidden his existence for 30 years.
Boxing Day sees Caleb and Cain's past explored, as the soap explains what happened between them in 1991 when Cain told him a devastating lie.
Cain claimed their mother Faith Dingle was dead and told him to stay clear of the Dingles - while Faith actually died 30 years later, in October this year.
While Cain's actions will be explained, Caleb will come looking for answers and it's teased he could take revenge.
Now, the cast and soap boss Jane Hudson have spilled on the special flashback scenes that feature a young Cain and Caleb.
Showing the moment Cain turns his back on Caleb, who is looking for his family, viewers will find out the truth - as the episode is set to "explain a lot".
Speaking to The Mirror and other press, actor Jeff Hordley who plays Cain revealed all about the special scenes, and what fans will learn about the past.
He said: "We have this flashback episode where you get to see young Cain and young Caleb when they first meet. The reason he said that their mother was dead, I don't know if you remember the episode we did in The Woolpack with Cain and Chas, and he talks to Chas about his coping mechanism for when his mum was letting him down was telling people his mum had died.
"That was his way of dealing with it so this is why he said it to Caleb, it's not just that she's dead, get lost, it's got a reason for it.
"We were lucky enough to get to meet [the actors playing the younger characters]. They watched us do a scene and then we watched them do a scene. The two young actors were absolutely brilliant. We need to see more of them."
On what the flashbacks will reveal, Jeff said the scenes explain why Cain doesn't trust his brother.
He said: "He's thinking I don't trust him because he's gonna want to do something to me. That's because of their short history that they had in these flashbacks, which explains an awful lot."
Soap producer Jane Hudson also spilled on the special scenes, revealing: "We’ve got Cain still in prison and he’s gonna get a visit from his brother on Christmas Day, Caleb played by Will Ash.
"I think viewers are gonna fall in love with him, you're all gonna fall in love with him very soon."
Revealing details of a special flashback, she went on: "So when Caleb visits him in prison we will discover that Cain knew Caleb existed, and has known about him for 30 years. On Boxing Day we will rewind to 1991 and discover how Cain and Caleb first met, why Cain then rejected him from his life and what was going on with Chas at that point.
"It's a brilliant episode that will explain a lot about their family history, and as much as Cain wants Caleb to disappear for another 30 years Caleb is not going to have that.
"He wants to meet Chas and meet the rest of his extended family, and could he be the answer to all the Dingles' prayers in regards to Cain being locked up? You'll have to wait and find out."
Emmerdale airs weeknights at 7:30pm on ITV1 and ITVX, with an hour-long episode on Thursdays.
