Leonard Horatio McCoy was hardly born named that, though it's his name now. This time around, he was born one John Grimm, made a marine and sentenced to a life full of goddamn misery and death, more than punishment enough for being a good man of good genes. He's tried many lives after that, some good, some bad, some downright evil, and some just about perfect. It's been a long road. This last life, he thought to settle down in Georgia, have a wife, a kid, but these things almost never work out for him. She took the entire damn planet, and his kids. Left him with a Bones, hurtling back into the space he'd come to hate alongside a kid who seemed dedicated to getting his neck broke.
Considering he's got nothing else to do, Bones figured he might as well try and keep this Jim Kirk alive.