At least one of them is male, according to the film's official novelisation.
"So, are we a match?" asked the fire guy.
When Cinder turned back toward the fire couple, they were embracing. She squirted them with the spray bottle "Save it for the wedding!", she spat.
"Hey", the fire guy sputtered.
In the film these two lines are not spoken by the same person, but the way it's worded in the novel suggests the two lines were originally intended to be spoken by a single (male) person, so we can probably play safe and presume that this is a heterosexual couple.
In the graphic novel , the smaller of the two individuals is rather more feminine-looking and it's the 'fire guy' who asks the question.