"That's a story," Miles said. "I didn't meet Mark until we both were adults. He's my clone-sib, and the person who had him cloned was planning on using him to pose as me to assassinate my father and the Emperor. Which, since it was before Gregor got married and we all had children, would have put me -- him -- on the throne. Thankfully, I talked him out of it."
Well, more that Ser Galen had been crazier than a colorful comparison and a nasty piece of work to anyone with the genes of Aral Vorkosigan Sr., including his own would-be assassin, and Mark liked amnesty and the promise of his own life more than being the method to throw the Imperium into chaos.