to Benedict, my brother who doesn't,
This is the clue. If it would have been
to Benedict, my brother, who doesn't,
Then he may have been the only brother the speaker has.
However, because there is no comma, the who doesn't is restrictive: in this case it describes an essential property of this specific brother. Since there is such a description for that specific brother, being the brother who doesn't live in Madrid, it follows there has to be another brother.
Since it is clearly stated there is only one other sibling, that sibling has to be male as well.
So not only do we know that Hilary is male, we know where he lives!
(Sorry for the earlier confusion. For more information on restrictive / non-restrictive clauses, have a look here.)
Since you're speaking in generalities, you can use the first person plural pronoun, even if you regard yourself as one of the exceptions (it's assumed that generalities can have exceptions). For example, I might say:
Us men, we never remember our anniversaries.
even if I happen to be a man who always remembers to make a reservation for our anniversary dinner well ahead of time.
I'm talking about men in general, and if I happen to be a man, that's the best way to say it – I should include myself in the first group, since I'm clearly a member of that group.
I suppose I could say:
Those men, they can never remember their anniversaries.
but that seems more fitting for a women to say, not a man. If a man says it that way, he's muddling the conversation, by creating three groups instead of two.
Since these kind of remarks are often intended to be somewhat humorous, we dampen the humor when we get so particular about the pronouns. It's better to be a little self-deprecating and include ourselves with the group, even if we don't exhibit the behavior.
When your friend says:
Indians are the worst drivers, we can take a turn from anywhere!
that's more likely to make me smile or laugh, whle:
Indians are the worst drivers, they can take a turn from anywhere!
sounds more like a peeve or a rant against others in a group that person belongs to, and some of the humor is lost.
Best Answer
We don't have widely-adopted gender neutral singular pronouns. The authors are trying to avoid using himself to describe both genders, and so use herself. This is quite a common practice. Other possibilities might be to say himself or herself, or customers can serve themselves.
See this reference for plenty of detail