He had genuine sympathy for the boy, so why not express it simply?

He shook his head, perhaps even in genuine sympathy.

She felt genuine sympathy for this creature, but was appalled by her nature.

She met his challenging tone with one of genuine sympathy, instead.

We come to feel a genuine sympathy for him.

It melted into genuine sympathy as he put a hand upon the small woman's shaking shoulders.

He smiled down at her, full of quite a genuine sympathy.

She was so convincing that the secretary looked at her with genuine sympathy.

Perhaps he was actually in more distress she thought, not without a pang of genuine sympathy.

Initial detachment gives way to genuine sympathy after seeing someone through so much.