The couple became engaged on New Year's Eve after Humes proposed during a holiday to Antigua with a ring believed to have cost £46,000.
Sources claim that Humes and Wiseman are hoping to coincide their big day with their respective birthdays on March 18 and March 21.
"After getting engaged this Christmas, Rochelle and Marvin didn't waste any time in thinking about dates," an insider told the Daily Star. "They knew they didn't want a long engagement that dragged on for months.
"Rochelle has been telling her pals how excited she is and that she loves the birthday idea. She thinks combining the events will make it the most amazing three-way celebration ever."
The couple began dating in February 2010, briefly split the following November and reconciled in early 2011.
Watch The Saturdays in the video for 'My Heart Takes Over' below: