Well, if you were to breed them, you would possibly have hundreds of babies that you might not be able to care for. This is if one of them were actually a female. BTW how big is your tank? Please tell me it's not one of those really small ones. I just saw that you aid it could be divided, so I immediately thought of the small one my cousin used to have her betta in.
The easiest way to tell is by how long all the fins are. Sometimes this won't work (if it's a PK it might be harder to tell for people like me XD). Also, if there is a white egg spot. Some males have this spot though, so it's not a definite way of telling.