Besides Ken serving a steroid suspension until January 2010, Frank in his latest interview appearance said his brother should "absolutely not" be fighting.
"You can tell he's cashing checks," Shamrock said Saturday on "MMA Nation" on 106.7 WJFK. "He's not bearing his soul, he's cashing checks."
The brothers signed a contract last year to fight on pay-per-view sometime in 2009.
"Fighting is a lot of ego, and that's okay," Shamrock said. "But you got to walk a fine line between what's ego and what's reality. And Ken's ego unfortunately has passed way into his reality and now it is his reality.
"I'm 36, I'm pretty broken and I see the end coming. Ken doesn't see the end and it's just silly."