The pair met when they were partnered together on U.S. TV talent series Dancing With The Stars in spring 2008.
However, they split after a year together, insisting they'd remain pals.
But the former lovers sparked rumours they have reignited their romance after they were seen getting intimate at a gay nightspot in L.A.
A source tells Radaronline.com, "They seemed to be having a great time, and they're definitely back on again…
"But at some point Derek must have had a really good look around the club, because he suddenly noticed that the majority of people there were men, and some of them hot young men half dressed. He then realised that they were in a gay club!
"It must have come as a total shock to him because as soon as he realised they hightailed it out of the club double quick."