The siblings, children of Martin Kemp and Shirlie Holliman, are among the contestants in the BBC reality show's third series, which involves a 3,670-mile race across Central America.
Other celebrity participants include Dylan Llewellyn with his mother, Anita Rani with her father, and DJ Tyler West with his girlfriend.
Roman learned from Harleymoon to embrace situations he cannot control, while she learned from him the importance of expressing emotions honestly.
The final episode, airing on Thursday, will see the pairs race to the finish line on the remote Peninsula de La Guajira in Colombia.