I have three guppies one male and 2 females. He doesn't mate with the females and when he gets near them the matriarch chases him away. Could he be terrified of them or something?
Have you just recently bought them?
Aggression and odd behaviour could be caused by water quality.
But it is normal for the male to mind his own business for some of the time and also the females to chase him away. Mine used to chase the male away all the time as he was half the females size, but he still managed to surprise them when they weren't careful