Complex sentence: Both Cato and Bibulus allied with Gnaeus Pompeius Magnus against Caesar, though both boni hated Pompey, he did not pose the threat to their faction that Caesar did.
Split into simpler sentences: Both Cato and Bibulus allied with Gnaeus Pompeius Magnus against Caesar. Though both Boni hated Pompey, he did not pose the threat to their faction that Caesar did.