There were at least a few dozen other Homo species. Homo sapiens, considered "modern humans", lived along side 8 other species at one point. They are all extinct now. Part of the reason is because of how well we adapted to a rapidly changing earth in the ice age. What seems like simple accomplishments now were monumental then, making ranged weapons, tighter fitting clothing, and being omnivores helped us dominate. The most famous cousin to us was Homo neanderthalensis, which were specialized in hunting big game. This hunting practice may of made them less adaptive and they had to travel great distances just to eat, which may of lead to their demise.