Giants may or may not stem from the same origins as smaller Humanoids, depending on who you ask. But they are able to grow much larger as their bodies are strengthened by the elements and nature around them. This makes them partially related to Elementals, but much closer to their smaller humanoid kin.
The largest giants can crush ta small building raised by small folk just by stepping on it. The smallest of them are still nearly twice the size of a regular person. As a general rule the larger the giant, the more respect it gets from its kin.