The highlighted phrase (Sunday Times, 4 January 2009) is wrong. Make it: ... her husband, of/about whom little is known. (About is the better preposition here.)
Prescriptivists wrongly believe that it is bad to end sentences with prepositions, and so would have us say That is the man about whom I was telling you rather than the more natural That is the man I was telling you about, with its preposition ‘stranded’.
The belief that preposition-stranding is bad is misguided, because it imposes an irrelevant feature of Latin grammar on English, resulting in sentences which sound overly formal.
But a formal, perhaps learned, tone was exactly what the writer was probably aiming for — except that, by the time she had got to the end of the sentence, she had forgotten that the second preposition was no longer needed.