Read "The History of Sir Richard Calmady: A Romance" by Malet, Lucas for free. A classic public domain work covering cousins -- fiction, lesbians -- fiction, mothers and sons -- fiction. Available in full text from Project Gutenberg.
Cousins -- Fiction
Lesbians -- Fiction
Mothers and sons -- Fiction
People with disabilities -- Fiction
Psychological fiction
Triangles (Interpersonal relations) -- Fiction
This book is in the public domain. Free to read and download from Project Gutenberg.