Three Sisters is the collective name for basic food crops that were planted by American Indians long before industrialized food production and farm factories came into being. The three foods were corn, beans, and squash. And these were the staples of life.
Clearly illustrated instructions on how and why to plant your own Three Sisters garden can be found here, along with a list of the optimum varieties of each Sister.
Heritage varieties, as well as history, can be found here. And, of course, good old Wikipedia.
I've made a couple of different versions of Three Sisters stew/soup. The first time, I made a soup stock from a smoked picnic bone with a fair amount of meat left on it and all the skin, as well. Lotsa minerals in the bone. And lotsa gelatin in the skin. Making the stock was no more complicated than putting the bone and skin into a kettle/cauldron/stock pot/dutch oven, keeping it covered with water, and simmering the hell out of it all day, while I did other things. Multitasking: I can do that.
Once I figure I've got every ounce of soluble nutritional benefit from the bone and skin, I discard them. Oh, you could give the bone to the dog, if you have one, but he won't thank you for it -- there's nothing left for him, not even flavor. It's all in the stock, where it belongs.
To this nice, richly flavored stock, I add: three 19-ounce cans of beans*, drained and thoroughly rinsed (this is important)**, about half a medium buttercup squash, seeded, peeled, and cubed, and some frozen kernel corn, using one of the empty bean cans as a measure. I also add a couple of chopped medium cooking onions, and maybe some celery, if I've got it. Yes, all at once.
That's it. I bring it to a boil, turn the heat down to simmer, and let it stew merrily away for about an hour, stirring occasionally, when I think about it.
Don't look for measurements. The kitchen is my playground, and I never measure anything.
The second version involves a vegan stock: cut the root end off a couple of cooking onions (red, yellow, or white, it does not matter which), leave the skin on, and cut them into quarters; put them in the stock pot. Follow that with a whole head of garlic, cut in half through all the cloves, and leaving the skins on. Add celery, carrot, wilted greens, whatever is in the fridge. If it's in your fridge, you must like it, so pop it into the pot. You can even add apple cores; I did -- I cut the core out of a quartered apple I was going to eat and just tossed it into the stock pot without thinking. It worked out just fine. Cover with water, bring to a boil, and turn down to a simmer. I added a few sprigs of fresh rosemary, basil, thyme, and parsley, and while it was making stock, it drove me and my neighbors crazy! About the only things I do not use for making stock are potatoes and other flavor-deadening vegetables like broccoli, beans, and cauliflower. I might put them in the soup or stew, but I never use them to make stock.
Vegan stock takes much less time than a meat stock -- about an hour, no more. Discard all the semi-solid vegetable matter (if you compost, it's perfect for that), and your stock is ready for use.
Then add the beans, the squash, the corn. If you like, you can also add freshly chopped onion and celery.
The number of combinations and varieties of the Three Sisters you can use are pretty much endless. And the amounts of each ingredient you use are pretty much up to you.
And it's always better the next day. If it lasts that long. Always.
*I use canned beans for two reasons. The first one is that it saves time and it's convenient.
The second reason is that with dried beans, their age will determine how long they need to soak and how long it takes them to cook properly, and there is no way to tell how old those beans are. I once tried for three days to cook some red kidney beans, before I gave up.
**Canned, dried beans like kidney beans and chick peas and others like them contain an enzyme that makes the beans ferment in the gut instead of digesting properly. This can produce the most excrutiating pain while it's on its way to producing the most obnoxious gas known to chemical warfare! Pour the canned beans into a colander and rinse thoroughly under running water until they stop foaming. Seriously. Your gut will thank you. So will your neighbors.