Gay Bully Guppies

One of my guppies was born with a spinal deformity. Two of the other males constantly harass him. The harassment is not fin nipping, but rather they seem to be trying to mate. They behave towards him the way males normally behave towards females. The fourth male joins in on occasion, but spends more time chasing the females. I have not witnessed the two antagonistic guppies attempting to mate with females at all. They are all siblings, born from the same mother at the same time. There are seven females in the tank, who seem starved for attention. Can anyone explain this behavior? It seems that I have two incestuous gay guppies, one bi-curious incestuous guppy, and a disabled guppy who strikes their fancy.