Complex sentence: Robert was most affected by his father's reaction to his eldest son's passing, who appeared completely heartbroken and it was commented by his peer Fred Garfield that Kennedy developed depression and questioned his faith for a short time.
Split into simpler sentences: Robert was most affected by his father's reaction to his eldest son's passing. He appeared completely heartbroken and his peer Fred Garfield commented that Kennedy developed depression and questioned his faith for a short time.