there many forms of Ghidorah most are cousins or brothers

Ghidrah(Showa) : (Ghidorah: The Three Headed Monster, Godzilla Vs. Monster Zero, Godzilla Vs. Gigan, Destroy All Monsters)

Dorats(Hesisi)(Baby Ghidorah): (Godzilla Vs. King Ghidorah (1991))

King Ghidorah(Hesisi): (Godzilla Vs. King Ghidorah)

Mecha-King Ghidorah(Hesisi): (Godzilla Vs. King Ghidorah, Godzilla Vs. Mechagodzilla II(1993))

Desghidorah (Death Ghidorah)(Hesisi): (Rebirth Of Mothra(1996))

Grand King Ghidorah(Hesisi): (Rebirth Of Mothra III(1998))

Orochi (Yamamoto No Orochi)(The Eight-headed Monster)(Hesisi): (Yamamoto No Orochi)

Cretaceous King Ghidorah(Hesisi): (Rebirth Of Mothra III)

King Ghidorah(Millenmium): (Godzilla, Mothra & King Ghidorah: Giant Monsters All-Out Attack(2001))

Keizer Ghidorah(Millenmium): (Godzilla: Final Wars)