Was that Clarke really in there somewhere? The Clarke who could look so gravely serious one moment and then burst into laughter the next? The girl who found everything on Earth miraculous, and kissed him as if he were the most incredible find of all?

He wanted to show her how to live, even after he was gone.

No matter how angry she was at him, she'd never deprive him of the change to see one of the ruins he'd spent his whole life dreaming about.

We live not for ourselves… it’s what my father always said to justify the sacrifices he had to make, like not spending enough time with me and Mom… or not marrying the woman he loved. But I never knew they had a child together.”
[...]
The dark outlines of the trees, the patches of star-filled sky, Clarke’s stunned expression, the nervous face of the kid Bellamy had once thought he hated, but now seemed to be… something else entirely. “So that makes you…”
“Your half brother.” Wells let the final word hang in the air, as if giving both of them time to examine the shape of it before they claimed it for their own. “I guess you and Octavia aren’t the only siblings in the Colony anymore.”
A laugh escaped from Bellamy’s lips before he had time to stop it. “Half brothers,” he repeated. “This is insane.” He shook his head, and with a grin, extended his arm and reached for Wells’s hand. “Brothers.

She would figure out how to get what she wanted, what she needed, even when her long lashes failed to convince, when her body was no longer young and beautiful. She'd be more than pretty, She'd be strong.

exhilaration fizzed through Clarke’s body. Before she realised what she was doing, she had thrown her arms around Bellamy. He joined in her laughter as he staggered backward, and wrapped his arms around her waist, lifting her up and spinning her through the air. The colours of the clearing swirled, green and gold and blue all blurring until there was nothing in the world but Bellamy’s smile, lighting up his eyes. Finally he set her down gently on the ground. Be he didn’t loosen his grip. Instead he pulled her even closer, and before Clarke had time to catch her breath, his lips were on hers. A voice in her brain told her stop, but it was overpowered by the smell of his skin and the pressure of his touch. Clarke felt like she was melting into his arms, losing herself in the kiss. He tasted like joy, and joy tasted better on Earth.