The Mark (слэш)

Prompt: AU where everything is the same, except everyone is born with a insignia, a mark that is unique to only two people in the world, that tells them who their soulmate is. Usually the two people are born on the same day, at the same time, but that doesn’t mean that aren’t circumstances where an age difference has happened.
Leonard McCoy was born without an insignia, only for one to appear on his 20th birthday. He always hated the idea that the one person he was supposed to be with being a child, and maybe that was why he married his high school sweetheart. And maybe, that was the fact their relationship fell apart six years later, and he made the choice to join Starfleet.
He had never really forgotten about his supposed soulmate, but it certainly wasn’t expected to be confronted with the seventeen year old Russian genius whose insignia, his insignia, their insignia, plastered so obviously on his neck…
I tweaked it just a little, but it's essentially that. Hope I didn't butcher the idea!