The ventrals tend to be very long in males, almost to the tail. But in plakats they are relatively short. It's hard to say as the flash is in the way of the beard, so can't tell whether or not it's showing. As well as the fins are not spread out- males tend to have large dorsal fins (in plakats) that are wide and almost roundish.
Honestly to me it looks female, is there a way to get a picture without the flash, as well as making it flare? You won't be able to tell by the aggression, as mentioned before females are very aggressive and by nature are solitary just like the males. We can just force them into being in a group under the right conditions.
Make sure your nephew has his tank very very densely planted, with plants reaching to the very top to help break up the lines of sight and give the females the comfort to go for air without being seen easily. A sparse tank, or tank only half full of plants will undoubtedly fail at one point and cause a lot of stress on them.