WHO LIVES IN '9 - DOWNING STREET' ?

We hear '10 - Downing Street' mentioned
time and again in media
because it is the official residence
of the British Prime Minister.
Do you know who lives in '9 - Downing Street' ?
If I say 'Nobody'
one may assume that
it being in the neighbourhood of
Prime Minister's residence
nobody is allowed to
stay there for security reasons.
But it is not the case.
Surprisingly there are only three numbered houses
in the Downing Street and they are 10, 11 and 12.
The Chancellor lives in and works from No.11
and No.12 accommodates offices
besides being the Government's Chief Whip's house.
There is nothing like houses
numbered from 1 to 9 !!!