Bach

I guess when people tag a track 'bach' it is Johann Sebastian they're listening to.
1685-1750
But, just in case... there is a nice family tree on the wiki page :
http://en.wikipedia.org/wiki/Bach_family

and the other lastfm Bachs :

nephews but forerunners?
http://www.last.fm/music/Johann+Michael+Bach
http://www.last.fm/music/Johann+Christoph+Bach
? http://www.last.fm/music/Heinrich+Bach 1615-1692
? http://www.last.fm/music/Johann+Ludwig+Bach 1677-1731

children, first wife
http://www.last.fm/music/Wilhelm+Friedemann+Bach
http://www.last.fm/music/Carl+Philipp+Emanuel+Bach
children, second wife
http://www.last.fm/music/Gottfried+Heinrich+Bach
http://www.last.fm/music/Johann+Christoph+Friedrich+Bach
http://www.last.fm/music/Johann+Christian+Bach