I wouldnt be surprised if it turns out that the Shadow Triad are actually clones of the Striaton Gym Leaders.

Ghetsis probably kidnapped them when they were a young age, took some of their DNA, proceeded to erase their memories of the incident, and then took them place to their home as if nothing happened.

The clones are then raised as Ghetsis' kids, are trained to become ninjas, and in due time his servants...

I know this is never going to happen but one can speculate, right? :)