Hi, four of J.S' own sons were outstanding musicians in their own rights.
Carl Philipp Emanuel was harpsichordist to Frederich the Great.  Carl
Philipp's elder brother, Wilhelm Friedemann, achieved renown as organist
in Halle, a position that had been rejected by his father years earlier.
Both were products of the union with Maria Barbara, herself a Bach and are
more prominently remembered.  But not forgotten are the progeny of Anna
Magdalena: Johann Christian who influenced Mozart, was music master to the
Queen of England and Johann Christoph Friedrich, court chamber musician at
Backeburg.

Check this webpage for more details:
http://jan.ucc.nau.edu/~tas3/familyhis.html

Franz Xaver was the only Mozart son who turned out to be a musician.

Luis