Traitors viewers were completely floored when Diane revealed that Ross is her son in Friday's episode of the BBC competition.
The duo entered the competition separately and did not reveal their connection with their co-stars, but viewers were let in on the huge secret in the third episode.
The unexpected revelation came after Zack shared his theory that Paul, a secret traitor, is Diane's son.
But Diane, 63, denied his theory and laughed it off, before telling viewers that she did indeed have a son on the show, but it was Ross, 28, instead of Paul.
The bombshell came after Game Of Thrones star Kerr Logan revealed that Diane is his mother when he took to Instagram to share his shock at her casting.
Traitors viewers were left completely floored when Diane revealed Ross is her son in Friday's episode of the BBC competition
Speaking to the camera, Ross confessed that he thought it would be difficult to hide their family connection when addressing the revelation.
He also hinted that his brother might be on the show when he responded to a fan's comment amid speculation about Diane and Paul before the real bombshell aired.
In response to the unexpected family connection, viewers took to X – formerly known as Twitter – to share their complete surprise.
One person wrote: “Ross and Diane are hiding their mother-son status from the rest of the group!”
While someone else shared: 'Diane and Ross, oh my Lord.'
Another surprised viewer wrote: 'What. Ross is her son. I do not believe it.'
“It's really hard for Ross not to accidentally call Diane mom,” someone else predicted.
Another viewer wrote: 'Assuming they want to keep it a secret the whole time, what price would you put on Ross making a mistake at some point and calling Diane 'mom'? It could be a game changer.”
“I thought some were related but didn't expect that,” another viewer wrote, while someone else shared, “Obsessed with Diane's camp plot twist.”
The unexpected revelation came after Zack shared his theory that Paul (pictured) – a secret traitor – is Diane's son, after which the retired teacher confirmed the truth.
Diane and Ross entered the competition separately and didn't reveal their connection to their co-stars, but viewers were let in on the huge secret in the third episode
Someone else wrote: 'Wait, omg, literally no one knows Ross is Diane's son?'
While another person joked: 'Give her a BAFTA for this NOW!!'
In the shocking scenes, Paul told Diane that Zack thought they were related, with the pair laughing at the speculation.
Anyway, Diane said to the camera: 'I can't believe it was suggested that Paul is my son. He's three times taller than me, he has red hair, Paul just couldn't be my son! But Ross does.”
Scenes then reflected on Ross telling his co-stars that his mother invited him to the show in the first episode, giving new relevance to his comments.
On the train, as the 22 participants all traveled to the Scottish castle, Ross said: 'Funnily enough, my mum actually set me up for it.'
He was also seen secretly talking to his mother Diane on the train before the other contestants arrived in previously unaired scenes, as they made plans on how to keep their connection a secret.
Ross said, “You know what the hardest part will be? I'll have to call you Diane.'
In response to the unexpected family connection, viewers took to X – formerly known as Twitter – to share their complete surprise
Speaking to the camera, Ross confessed that he thought it would be difficult to hide their family connection as he addressed the revelation.
“I thought I was going to make a mistake all the time, to be honest. At the end of the day, we are a team and we are going to divide and conquer,” he said.
'We have the competitiveness and the drive to win one of our own. If one of us wins, we both win. We're going to keep the relationship a secret.'
Previously aired scenes also flashed on to remind viewers how Diane Ross had advised who to vote for, hinting at their teamwork in an effort to win the prize money.
“I think you have to be very careful about voting for people that other people agree with because then you are challenged,” she told him.
Diane was then seen talking to Zack about his theory that Paul was her son, while Ross stood next to him.
Diane said cryptically, “Do you think my son is in this game?” with Ross feeling awkward between the two of them.
Zack then said, “I think you and Paul look a little alike!” prompting Ross and Diane to fall into fits of laughter.
Ross was seen secretly talking to his mother Diane on the train before the other contestants arrived in previously unaired scenes, as they made plans on how to keep their link a secret.
It's not the first time there's been a secret connection on the show, as last year Alex Gray and Tom Elderfield hid the fact they were a couple
Zack explained that because she and Paul are both ginger, he thought they might be related, with Diane then clarifying that she dyes her hair.
The mother-son duo has so far managed to hide their connection from their fellow contestants.
It's not the first time there's been a secret connection on the show, as last year Alex Gray and Tom Elderfield hid the fact they were a couple until dramatic scenes where Tom told their co-stars.
Diane's link with Ross comes after another of her surprising family connections was revealed when Game Of Thrones actor Kerr Logan confirmed she was his mother.
Kerr, 35, posted an official photo of her from the show before the debut episode aired and shared his excitement about her appearance on the programme.
He wrote: 'My mother is on the traitors. My mother is on the traitors. My mother is on the traitors. She is crazy. I'm afraid.'
Kerr – who starred as Matthos Seaworth, son of Ser Davos, in the HBO adventure series – claimed he only found out his mother would be in the show when the cast was officially revealed just days before the series kicked off .
Posting the official group photo, he wrote: 'How are you supposed to react when your immediate family is in this photo and you've just discovered it like the rest of Britain?'
To which Diane cheekily said, “I'd say, Wow, that's absolutely amazing!!!”
Fans were quick to respond by joking that his brother was on the show amid Zack's speculation about Paul – with Kerr hinting at Ross' true identity in response.
One fan wrote: “And your brother too,” prompting Kerr to hint he wasn't far off the mark as he replied: “Shhhhh…”.
Diane's link to Ross comes after another surprising family connection was revealed when Game Of Thrones actor Kerr Logan confirmed she was his mother
Kerr played Matthos Seaworth, son of Ser Davos, in the HBO adventure series (pictured) and has also amassed credits in Holby City, Victoria and The Killing Kind
Kerr claimed he only found out his mother would be on the show when the cast was officially revealed, just days before the series started
He also hinted that his brother might be on the show when he responded to a fan's comment amid speculation about Diane and Paul before the real bombshell aired.
The Traitors sees 22 strangers play the ultimate game of detection, backstabbing and trust, in the hope of winning up to £120,000.
In the show, most of the contestants are Faithfuls and they must figure out who among them are Traitors – who have the chance to 'kill' a fellow contestant every night.
The group has daily 'bans' in which they must vote to kick out someone they believe is a traitor, while working together on challenges to raise money for the prize fund.
In addition, the participants compete in various 'missions', which until now have aimed to increase the prize pool, but this year can also see the group win 'shields' that protect them from murder for one day.