Identical composers?

Could someone here explain the difference between John Adams and John Luther Adams? They are both roughly the same age, both American, both use a watered-down minimalist style, both have a new-age and spiritual quality to their work, both use lots of percussion, both are highly acclaimed, and both have won awards. Both also seem to have an image as 'sociable outsiders'? It's bizarre that two composers are so similar? Is this unique or do other composers have an uncanny similarity with each other?