Kevin or San! - Demi Pansexual 

He is the youngest head of the group. His horns are heart shaped and more curled

Ni - Demi Straight Ally

He has dyed his teeth as a symbol of being the warrior head with asteroid tears or the dust off a asteroid. His horns are more Chaotic 

Itchi - Demi Bi

The lead head who horns are twirled to symbolize infinite and unison. He has the most spikes and the more vicious look

In my headcanon Ghidorah is the Ruler of his species and with the fused horns symbolize his royalty. He can also emit control over the other space hydra like a queen Ant