After extensive and exhaustive research, I have come to the terrifying conclusion that actors Ethan Hawke, Josh Brolin, Craig Sheffer and Stephen Dorff are actually the same person. This is why we've never seen them co-star in the same project together...besides the fact that no one would care to.
Currently, the "Josh Brolin" personality is in control & having a career. The "Ethan Hawke" was dominant, until he made the unfathomable mistake of cheating on Uma Thurman with their nanny and has been banished to where "Craig Sheffer" and "Stephen Dorff" have been since "A River Runs Through It" and "Blade" respecively.
For a brief time, it was believed that "Paul Walker" was also part of HawBroDorSheff (as he was known in the lab where he was grown), but it was later determined that "Paul Walker" was a mass hallucination by the American public caused by an overexposure to Vin Diesel's machismo.
If you encounter HawBroDorSheff in the wild, don't panic...he's not used to being recognized, so he's really not dangerous. Just don't mention the Uma affair...it makes him cry.