William died on July 17, 1944, of a cerebral hemorrhage leading to pneumonia. Anxious to avoid the presence of the gaping press, Sarah hastily arranged the funeral, which was held at Portsmouth the following day. She allowed only a handful of friends and relatives to attend. William was buried next to his father at Harmony Grove cemetery in Portsmouth.
Father : Boris Sidis 1867 - 1923, aged 56
Son: William Sidis 1898 - 1944, aged 46
Mother: Sarah Mandelbaum Sidis 1874 - 1959, aged 85
Sister: Helena Sidis 1908 - 1995, aged 87
