So, it turns out despite a previous rumor, galactus is not a unique being in the multiverse according to the barside buzz. On many occasions we've seen a galactus from another universe, which seems to indicate that each universe has its own galactus Galactus on the other hand has a common origin for all his multiversial instances
He is the one and only survivor of a previous incarnations of the multiverse. Each new multiversal iteration brings complexity and new concepts, with characters like galactus playing crucial roles in the cycle. What to expect image source
But, in doctor strange in the multiverse of madness, we got the idea that there is only one america chavez in the entire multiverse. Marvel's multiverse is a living entity that experiences growth, death, and rebirth, with each iteration represented through cosmic beings