Stargate Atlantis: The Sheppard Twins

Soulmates exist! When it's discovered that John Sheppard has the Ancient gene his twin's DNA is tested and found to carry the Ancient gene as well. Doctor Weir immediately asks John to have his twin fly back home to see if he would be willing to go on the Expadition as well. Randy, to Doc Weir's surprise is John's twin sister who is one of the few people born with two soulmates..