Scars & Starlight by Liana Valerian

Tara’s life is a battle for survival in the ashes of a fallen world. When her camp is overrun by alien invaders, she braces for the end – until a mysterious new species descends from the sky and obliterates the threat in moments, rewriting the rules of war.
The Avaren are terrifyingly advanced and devastating in battle. At their head stands Kairen, a celestial enigma: beautiful, unreadable, and far too gentle for someone who commands an army.
With a galaxy of secrets between them, Kairen hides the truth: Tara is his genetic match – the one partner fate has carved out just for him. But before he tells her, he plans to earn her trust… and maybe her heart.

As they join forces to reach Earth’s scattered leaders and push back the Ghorvek threat, sparks fly. Because surviving the end of the world? That was just the beginning.