Board Thread:Movie Discussions/@comment-24106134-20150112142258/@comment-25285745-20150315080036

Meeston Falcon wrote: GodzillaIsland7.2 wrote:

The egg could have belonged to another creature of Godzilla's species before it died very long time ago. Or maybe mutated by radiation (same event in GvMG 1993), Baby Godzilla was Rodan's son. but he was mutated into a baby Godzilla.

They state in the movie that Baby Godzilla was a Godzillasaurus egg that was either stolen by a pteranodon or placed in its nest by its mother. Rodan was born in the nest, and thought Baby was his brother. When Baby was born, he was unaltered by radiation and was still a Godzillasaur. He didn't become mutated until after he was adopted by Godzilla and living on Birth Island.