The translation "humane boy" sounds funny, and is not used as such in English. The correct translation might be "understanding boy".
Agreed, it sounds odd. Usually people are described as "compassionate," while acts are described as "humane." E.g. a "humane execution" rather than a "compassionate execution."
Humane-ity is in general decline: http://books.google.com/ngrams/graph?content=humane&year_start=1800&year_end=2000&corpus=15&smoothing=3&share=
Although it may be seldom/never heard or spoken, I believe it works for the purpose for which it is used, such as he shows compassion whereas 'understanding' doesn't necessarily mean he is compassionate. Est-ce que vous acceptez...un peu?