Darcy/Jane/Thor
Ever since Darcy was old enough to understand the concept of soulmates she knew she had two, as evidenced by the writing and drawing that appeared on her skin regularly.
Darcy also knew that one of them was called Jane, was a girl and also VERY smart. She also knew that they shared her other soulmate, who was a complete mystery to them since his(they assumed that he was a he based on the shape of the writing) writing and messages were in a weird runic language.
Meeting Jane was great, she could finally put a face to the name, their third was still a mystery until a couple of days after Thor crash landed into their lives.
It was a normal evening, except Jane was on the roof talking science at Thor, it was relatively normal until Jane’s excited screech pierced the air followed immediately by Jane calling out to Darcy.
"Darcy! Get your ass up here! You need to see this!"
"Coming boss lady!" Darcy dragged herself up to the roof where an excitedly bouncing Jane grabbed her arm and dragged her over to Thor.
"Watch this!" Jane practically yelled before pulling a marker from her pocket and painting an X on the back of Thor's hand. She then lifted Darcy's hand up and put her own next to it, and Darcy watched as matching marks blossomed on the backs of their hands.
"Oh." Darcy breathed "well i guess I better sit here with you and learn something don't I?"
Their marching smiles were all the answer she needed.