Complex sentence: Although the Gilbreths'work is often associated with that of Frederick Winslow Taylor, there was a substantial philosophical and personal rift between the Gilbreths and Taylor; after Taylor's death, the feud continued between the Gilbreths and Taylor's followers.
Split into simpler sentences: Although the Gilbreths'work is often associated with that of Frederick Winslow Taylor, there was a substantial philosophical difference between the Gilbreths and Taylor. This led to a personal rift between Taylor and the Gilbreths, which after Taylor's death turned into a feud between the Gilbreths and Taylor's followers.