The Channel 4 drama's forthcoming 'flashforward' episode will see the estranged couple, played by Whittle and Gemma Merna, enjoying their second wedding day.
However, in a tragic turn of events, Calvin will end up being shot dead by a mystery assailant in the dramatic instalment, which is set in May 2010.
Discussing the pair's surprise reunion in an interview with DS, Whittle explained: "Calvin's completely besotted with Carmel. She's the one he's always wanted - she's always been his true love since they first started seeing each other and everyone's always wanted them to get back together, which has been nice.
"I think it's a very good example of fan power. The producers weren't going to put these two together ever again because everyone wanted them together. It was a Ross and Rachel situation - they're meant to be [together], but something would always happen for it not to quite work out."
He added: "I think Calvin and Carmel fans will be happy that they're back together in the episode - it'll just pull a few heartstrings when Calvin's shot at the end."
The Chester-based show's recent episodes have seen Calvin embarking on a secret affair with Carmel's sister Mercedes Fisher, played by Jennifer Metcalfe.
Hollyoaks' 'flashforward' episode airs tonight at 6.30pm on Channel 4.
> Click here to read our interview with Ricky Whittle
> Click here to read more from Ricky Whittle in Soap Scoop