Children of the Enaisi (Sword's Edge Chronicles)

Marcalan is haunted by secrets. He learned early on not to tell anyone about his alien ancestry. It would only bring shame on his family if people knew. Not to mention the trouble he'd be in if anyone found out he's dared to fall in love with his Thane’s niece.
As for her, Tam is unsure of herself, and now, living in the city where she's heir to the Thane, she feels even more alone, especially with her alien abilities. Her uncle is determined to use her to access the fabled portal and its secrets.
Opening that portal could change the world: literally change it. On the other side is the technology of the aliens whose DNA gave Marcalan and Tam their special gifts and could bring to their people advanced technology and advanced civilization, and the loss of everything they love.
They could lose control of their secrets.
They could lose one another.
They could even lose their lives.