The small boy obviously didn't believe you could be so kind. He shot you a sidelong glance and continued his work.
"Because I see you're working so hard. If you tire yourself out, your parents will be heartbroken."
"Hmph, they wouldn't care about me. Now that they've had a chubby little brother for me, they won't love me anymore. They even said they'd feed me to a tiger."
You thought to yourself, "Here's the quest," then used a comforting tone to say, "Even the fiercest tiger wouldn't eat its own cub. And we're humans, not tigers. Since you're their flesh and blood, they won't abandon you, let alone feed you to a tiger."
"I heard them say it with my own ears!" The boy's eyes began to water, and then tears started pouring down like rain. "They're so cruel, big brother! If you help me kill my little brother, I'll give you something nice!"
A trace of malice flickered in the boy's eyes as he said this.