Let's start with the list of nightshades. (Scroll down this page to see the complete list.)
This plant family includes popular vegetables, poisonous plants, and drugs. An overview: potatoes, tomatoes, chili peppers, bell peppers, eggplant, tobacco, belladonna, and jimsonweed.
The plants in this family manufacture drug-like chemicals (of a kind called alkaloids) in their tissues--in the leaves, roots, flowers, and fruits. The most well-known of these alkaloids is nicotine.
America's favorite vegetables--potatoes, tomatoes, chili peppers--also contain drug-like alkaloids. They can cause pain or affect the central nervous system in some people.
Foods in the same family are related.
A family is subdivided into genera (the plural of "genus.") Foods in the same genus are even more closely related.
Ketchup / Catsup sauce
Tamarillo / Tree tomato
Bell peppers / Green peppers / Sweet peppers
Chili peppers / Hot peppers
Examples of varieties:
Ancho (dried Poblano)
Chipotle (smoked Jalapeño)
Pimiento / Pimento
Powder blends and sauces:
Curry powder - most contain chili pepper
Goldenberry / Cape gooseberry / Inca berry
Goji berry / Wolfberry
Belladonna / Deadly nightshade
Datura / Jimsonweed