Ciarran went on to become a fan favourite on Angie Kent's season, but pulled out after receiving the tragic news that his grandmother had died.
He and Renee appeared to patch things up after his stint on the dating show and the two were even went on holiday to Bali with some other Bachelor/Bachelorette alumni, including Niranga Amarasinghe who's also starring on season three of Bachelor in Paradise.
Fan account Bachie Funny even uncovered a snap of Ciarran and Renee captioning it: "Looks like someone's back with his ex (from Matt's season) and won't be the next Bachelor after all Nov 2019."
By September 2019 though, things went south once more with an insider telling Daily Mail Australia that Ciarran became "distant" and broke things off with Renee when casting began for Bachelor in Paradise season three, leaving Renee "heartbroken."
Now, it appears that Renee is the ex crashing Paradise as an intruder and Ciarran himself has admitted he's not expecting "the best edit ever" this time round.
"I think I'll go from the sweetheart of Australia to the bad boy of Australia so that won't be good," he told British newspaper Manchester Evening News.
"It's called Bachelor in Paradise but I went on and it was like Ciarran in Paradise! Every girl took me on a date and I was absolutely loving it.
"My ex-girlfriend was on there as well which isn't ideal and I just thought I was on Love Island so was trying to get with every bird possible."
As seen in trailers, Ciarran enjoys a fling with Abbie Chatfield and potentially Jessica Brody who's rumoured to join the cast as an intruder.
But the drama is set to amp up upon his ex's arrival in Paradise who reveals in the latest promo: "People don't actually know what happened between Ciarran and I."
Ciarran even storms off from a group dinner exclaiming "F*** this I'm going home," after his "lying" is exposed to the rest of the group.
We can't wait to watch and see what happens!