That is until until they were reunited on ITV2 show Secret Crush.
Maddie went on the show to reveal her true feeling to ex step-brother CallumITV
Over the years, the pair had kept in touch via social media where Maddie said her feelings for her former step-brother had developed.
She then decided to take the plunge and confront him on the TV dating show.
At the beginning of the episode, Maddie said: “I’m here to tell my brother that I fancy him. Just to be clear, we are not related - my mum and his dad were together many years ago.
“But since we got back in touch on social media he’s really matured and he’s very good looking.”
Maddie described how one conversation they had started getting “a bit flirty” and that’s when she realised “maybe it’s a bit more than step brother and step sister.”
She added: “I feel quite nervous about telling him but I’m also quite excited because I’d be interested to see what he thinks and what he has to say. If this goes badly I think we can say goodbye to any future family reunions, but hey ho.”
Before the show, Callum was completely unaware of Maddie’s feelingsITV
Meanwhile, Callum, a stone mason from Essex, was completely clueless about Maddie’s romantic intentions.
However, he couldn’t hide his shock after Maddie emerged as his date for the evening from behind a velvet curtain.
Blushing, he said: “I can’t believe it’s you. That’s mad, that’s crazy. You were the last person I expected to walk though that door.
“I (haven’t) seen you in years, we haven’t even spoke that much - you’ve kept it a right secret. I’m blown away to be honest.”
Over an awkward drink, Maddie explained her crush to him.
“You’re just sound and genuine. You’ve really matured since I last saw you and I was like yeah, I want to meet you,” she said.
They then addressed the elephant in the room - the legality of the relationship.
Callum replied: “Basically we were not even step brother and sister because (our parents) didn’t get married.”
Maddie pointed out that they were engaged, he says: “Yeah, but they didn’t get married. We’re not doing anything illegal so it’s all sweet.”
But the question we all want to know the answer to is - how will their parents react to this bombshell?
Maddie admitted her mum was shocked when she told her about the date, while Callum shared what his dad might think.
“I think my dad would probably be a bit lost for words. I don’t know how he’s going to take it but you know what, I don’t care - it’s not about him, its about me, about you,” he said.
So...what was the verdict on the date?
Speaking afterwards, Callum said: “As long as she treats me well and can cook, maybe I will get down on one knee and propose. I can’t believe she had a crush on me, she was the last person I expected to be interest in me whatsoever.
“It’s crazy to think that after all these years I’ve still been in the back of her mind somewhere, that’s a compliment in itself.”
Maddie said: “He was really shocked, he had no idea it was me at all.
“I think that was one of the best dates I’ve ever had, we really clicked and got on well. I was really nervous, but I think it went really well. I’m excited to take him home to meet my mum, I can’t wait to see the reaction and the look on her face.”
You can watch ITV 2’s Secret Crush, hosted by by comedian Verona Rose online.