Bigendered people don't categorize into male or female, they more accurately qualify as male and female. Often such people will present as one gender in one circumstance only to present as the other in another. To them, both presentations are equally valid. Often, bigendered people don't have a preference to pronoun use, being fine whichever way they are used. Indeed, some will encourage pronouns to be mixed within a sentence.
In the superhero genre, bigendered individuals tend to be shapeshifters, who can completely alter their appearance to the other gender and sex at any time. However, not all shapeshifters qualify, because this is an identity category. For instance, Mystique may take male forms from time to time, but she very clearly identifies as female, and one would treat her as such. However, Xavin will change between the two interchangably without distinguishing either as the "true" form, making that character fit into this category.