Godzilla's Family Tree.
The King of the Gods is not entirely alone in the world.
His "Family" is as follows.
Godzilla "Junior"- This is widely considered Godzilla's son. Truth is they are not truly related. Junior is another separated Godzilla, although nowhere near his power level. This one is not a Destroyer, instead he has taken the path of a peaceful existence, fighting only when needed to. Godzilla, despite his destructive nature, protects this one and is a close friend.
Biollante- This massive Goddess is none other then Godzilla's younger sister. She was created by sciences that included Godzilla's DNA. This is where the family link ends. Biollante is more Plant then she is Godzilla, and she is a protector, and savior of nature. The two do regard each other as family, but the relationship is, at best, cold.
SpaceGodzilla- This demon is related to the King much in the same way Biollante is. A younger brother created when the King's cells were thrown into space. Spacegodzilla, however is nearly all evil, and his hate for his older brother is legendary. Despite being related they do despise one another. SpaceGodzilla will do anything to kill Godzilla.
Kiryu- This is an oddity. The machine god was created long ago, but its structure, its skeletal structure is that of none other then the very first Godzilla that appeared on the planet, and was killed. The bones were coated in steel and it was reborn into the machine god. Godzilla is "related" to this beast, but it is a secret known to very few. To the rest of the world Kiryu is just a likeness of the king, nothing more.