By Reeta Chakrabarti
BBC News political correspondent
Derek Conway has fallen foul of the parliamentary watchdog for the terms on which he employed his son.
Mr Conway is one of dozens of MPs to employ family members
But MPs taking on members of their family to work on their staff is not at all unusual.
Many have to spend the working week away from home.
Employing your wife - and sometimes your husband - must seem like killing two birds with one stone: you take on someone you trust, and you get to see more of them.
It is impossible to know precisely how many MPs employ family members - but a non-exhaustive study suggests probably more than 40 out of the total 646 have a spouse, child, or even a parent on their staff.
Not all are necessarily paid.
MPs can be rather coy about admitting to employing family - but some arrangements are long-standing.
Leo Beckett, the husband of the former foreign secretary Margaret Beckett, has worked on his wife's staff for many years, currently in the role of office manager.
The basic guidance for MPs taking on staff is contained in a handy little booklet called the Green Book.
Iain Duncan Smith employed wife Betsy
Details of the pay ranges for staff - family or otherwise - and what they might be expected to do for their money are laid out on the parliamentary intranet.
Junior secretaries (recommended starting pay between £20,000 and £28,000) should have a "polite and courteous manner" and good keyboard skills.
Research or parliamentary assistants (starting pay £26,700 to £31,700) should be graduates, with a "good understanding of the political environment".
But these are guidelines only, and MPs are left to make their own decisions about whom they employ and what they are paid, within their parliamentary allowance.
Last year that was around £87,000.
What is expected is that anyone employed by an MP and paid for out of the staffing allowance must be carrying out parliamentary work.
The most high-profile case of a family appointment was that of Betsy Duncan Smith, wife of the then Conservative party leader Iain Duncan Smith.
An allegation that the pay she received was not in line with the duties she carried out was not upheld by the parliamentary watchdog.
Although Mr Duncan Smith was exonerated, the case was the first to highlight the practice of MPs employing family members.
If Derek Conway is suspended from the House of Commons, as the parliamentary committee recommends, he will, records suggest, be the first in more than 50 years to be barred because of misusing his staffing allowance.
One suspects that, following his very public rebuke, MPs might well be reaching for their Green Books to remind themselves of the rules.