John Harrison has told me about six (see below). Does anyone know of anymore?
Solanaceae - The potato family - potatoes, tomatoes, aubergines
Cruciferae - The cabbage tribe - cabbage, cauliflowers, kale, turnips, radishes, swedes
Umbelliferae - carrots, parsnips, parsley, celery, celeriac
Liliaceae - The Lily family - garlic, onions, shallots, leeks
Leguminosae - The bean family - legumes, anything with bean in it, peas
Cucurbitaceae - The cucurbit family - cucumbers, marrows, courgettes, pumpkins