I've reported the English sentence as awkward. To quote from Wikipedia (https://en.wikipedia.org/wiki/Brown_hair)...

> Brunette literally means "little brown-haired girl" or "young brown-haired woman", but, in modern English usage, it has lost the diminutive meaning and usually refers to any brown or black-haired girl or woman, or the associated hair color. [...] Although brunet is the masculine version of the popular diminutive form used to describe a little boy or young man with brown hair, the use of brunet is uncommon in English. One is more likely to say of a man or boy, "He has brown hair" or "He is brown-haired", than to say, "He is a brunette" (or brunet). The term brunette is the feminine form of the French word brunet which is a diminutive form of brun meaning "brown/brown-haired", the feminine of which is brune. >

I strongly agree with Carl and I would say that in British English one would never call a man/boy a brunette. A brunette is always a woman/girl with brown hair. For a man/boy just say that he has brown hair. I would also suggest avoiding calling a man/boy a blonde or a redhead, although these are less definitively wrong and they might sometimes be acceptable in the right company. (OK, perhaps this is sexism that we have not broken free of yet.)