I decided to do this a little differently; it's not about the two falling in love, it's more about their relationship. I hope you enjoy it! Oh, and, uhm, POTENTIAL FEELS WARNING. Please review!
Tears streamed down Tonks' face as she ran through the castle, sending spells and curses at any who tried to attack her or get in her way. She had only one thought in mind: Remus. She knew she had to find him, to see him, to assure him she was alright, and to be assured herself that he was unscathed.
The gold wedding band on her hand sparkled as it reflected the light from the various curses in the room; she was forced to duck and cover her face countless times as the walls around her crumbled. She ran and struggled until she felt she could move no more; her body was heaving with sobs and screams of anguish were escaping her mouth. "Remus, where are you?!"
Then, she shook herself mentally, stopping (perhaps dangerously) in her tracks. What was she doing?! She was an Auror, for God's sake! She had fought dark wizards before and stayed strong, how was this any different? She forced this question to hang in the forefront of her mind, although she already knew the answer – this time, her soulmate was at stake. Plus, it probably didn't help that her hormones were teeming all over with the baby. Teddy…
She swallowed her tears with some difficulty, then set off once more, her wand clutched tighter in her hand. She would find him. He would be perfectly fine; surely she would know if he had been hurt, surely she would feel it in her heart. Barely a second after this thought had passed through her mind, cheering her up slightly, she saw him. And he saw her.
She ran towards him, stumbling a little over the debris on the ground. Remus was fighting a Death Eater and although he was not losing, he was not gaining an advantage either. In one swift, fluid motion, Tonks lifted her wand and shot a Stunning Spell at the unexpecting Death Eater; he fell to the ground with a thud. Remus turned to his wife and grinned. "Good shot." He reached out to wrap his arms around her waist, pressing his lips to hers.
Then, the unthinkable happened.
Just as they pulled away, still clutching hands, the air exploded. The castle wall collapsed, and the couple fell together, their hands still entwined.
Tonks' last, slightly comforting thought was at least they were together, and hopefully Teddy would not be alone; at least one of her friends must live, surely, and would take care of him.
And then, Remus and Tonks took a few last, short breaths, using their final stores of energy to turn their heads towards each other. And then they died, staring into each other's eyes, hands held tightly.