The Space Giants

The alien invader Rodak plots to conquer the Earth. He first warns the Mura family (father Atsushi, mother Tomoko and son Mikko) of their invasion, and demonstrates his powers by transporting them to a prehistoric jungle and destroying a Giant Dinosaur (in reality, Agon, the title monster of a serialized Godzilla-like TV movie.) before their very eyes. But they will not agree to surrender to Rodak, so hope comes in the form of Goldar, an armored, golden giant with long hair and antennas. He and his human-sized wife Silvar, both created by the wizard Earth (who sure enough lives deep beneath the Earth), are sent to defend our world against Rodak. They befriend Atsushi and Mikko, the latter has Rodak emotionally touched, as he wanted to have a child with his wife Silvar, so Earth creates a duplicate of Mikko, named Gam (who wears a helmet with antennas). Earth gives Mikko a whistle, with which he can call Gam (when blown once), Silvar (when blown twice) and Goldar (when blown thrice) in times of crisis. So when Rodak unleashes his various daikaiju, chances are, Goldar, Silvar and Gam will fly to the rescue.