Complex sentence: Johnson remained with his close friend Harry Porter during a terminal illness, which culminated when Porter died on 3 September 1734, leaving his wife Elizabeth Jervis Porter (otherwise known as "Tetty") widowed at the age of 45, with three children.
Split into simpler sentences: Johnson remained with his close friend Harry Porter during a terminal illness, which ended in Porter's death on 3 September 1734. Porte'r wife Elizabeth Jervis Porter (otherwise known as "Tetty") was now a widow at the age of 45, with three children.