Acari
Acari are mostly a group of ticks and mites that are very closely related to spiders such as the camel spider. In terms of biological relation, size makes no difference, meaning a tiny parasitic deer tick can be closely related to even a massive predatory spider. The acari are classified as being close relatives to camel spiders because of their similar body structure of eight legs, no rear-leg claws or spines and similar internal structure.
Opiliones
Opiliones are an order of arachnids commonly known collectively as harvestmen. Despite camel spiders being vicious hunters, opiliones include such creatures as the "daddy longlegs," which are small spindly spiders that are completely harmless to humans. Opiliones often possess long walking legs compared to their body size and a more oval-shaped body, given that their head and abdomen are broadly joined and less distinct than the likes of a camel spider.
Scorpions
Much like the camel spider, scorpions are known for being aggressive predators in the arachnida class. Despite widespread fears and rumors to the contrary most scorpions, like camel spiders, do not have venom capable of killing a human being. Of the approximately 1,752 species of scorpions, only 25 posses lethal doses of venom. Scorpions can be found in many of the same desert climates as camel spiders, although scorpions are far more widespread and exist on every continent except Antarctica.
Pseudoscorpions
Pseudoscorpions are less predatory than scorpions and usually significantly smaller, although their physical structure is largely the same, making them close relatives of camel spider nonetheless. Pseudoscorpions are behaviorally different as well. While camel spider and scorpions hunt their prey, pseudoscorpions are more akin to acari and will feed on moth and beetle larvae as well as booklice, ants and small flies. They possess similar pincers to scorpions and round bodies similar to camel spider's abdomens.