-Sex: the manifestation of Catherine's desires in her dreams in Northanger Abbey, eroticism and corruption in the Monk.
-Incest: the Castle of Otranto (Horace Walpole 1764), Isabella preyed on by father-in-law, Manfred. Rebecca's relationship with her cousin.
-Homosexuality: relationships between Basil/Henry/Dorian in the Picture of Dorian Gray (Oscar Wilde 1890) linked to Oscar Wilde's own homosexuality, homoeroticism in both Dracula and Jekyll and Hyde.
-Polygamy: Jane Eyre (Charlotte Bronte 1847) discovers that Mr Rochester is already married and hiding his wife in his attic.