Complex sentence: While it is almost certain that he caught the disease through sexual intercourse, it is not known whether or not he had caught it through homosexual or heterosexual sex; however, some of his physicians suspected that Robert was gay.
Split into simpler sentences: While it is almost certain that he caught the disease through sexual intercourse, it is not known whether or not he had caught it through homosexual or heterosexual sex. However, some of his physicians suspected that Robert was gay.