Complex sentence: Cabot did not halt his other film and television work during the run of "Family Affair"; he took a leave of absence from the series at one point; his replacement was veteran British character actor John Williams, who played French's brother Nigel.
Split into simpler sentences: Cabot did not halt his other film and television work during the run of "Family Affair", though he did take a brief leave of absence. During this time, he was replaced by veteran British character actor John Williams, who played French's brother Nigel.