Complex sentence: In April 1963, his father, who had been ill with diabetes and heart problems, committed suicide, leaving behind a suicide note asking that Charlie, who was already married with a child, take care of his mother and siblings.
Split into simpler sentences: In April 1963, his father committed suicide due to being severely ill with diabetes and heart problems. Leaving behind a suicide note, he asked that Charlie--who was already married with a child--take care of his mother and siblings.