Cellmates — Robert A. Burton

Imagine: You've just found out you have nine brothers.  Identical to you in every way.  Except for the gene that made one of them a killer--

Artie Singleton's mother was dead.  But among her possessions lay a letter.  And inside was a secret that would shatter her son's world: In 1963, a shocking experiment at a famous fertility clinic had cloned ten identical male children from a single donor embryo.  Artie Singleton was one of them.

Artie, a successful San Francisco entrepreneur, is now searching for his nine brothers.  He assumes they will look just like him.  But Artie finds some things he didn't expect: a sociopath among the clones determined to kill off the others--and a terrifying truth about their gene pool that could spell Artie's doom, or give him the cunning to stay alive.