Robin Hobb finally explains it in Dragon Haven, book 2 of the Rain Wild Chronicles, that the others are the offspring of 2 dragons that both have been too close too humans (Elderlings) for to long. Other's island is where the dragon lay their eggs, which usually hatch into serpents, which go to the ocean for a time to grow, then travel to the Rain Wild River, to cocoon on the banks of the Rain Wild River (in what humans call wizard wood), to emerge as dragons.

Robin Hobb finally explains it in Dragon Haven, book 2 of the Rain Wild Chronicles, that the others are the offspring of 2 dragons that both have been too close too humans (Elderlings) for to long.

Other's Island is where the dragon lay their eggs, which usually hatch into serpents, which go to the ocean for a time to grow, then travel to the Rain Wild River, to cocoon on the banks of the Rain Wild River (in what humans call wizard wood), to emerge as dragons.