I need a gluten free, dairy free, soy free, soy free, corn free, meat free dish that is also low sugar and cannot contain any citric acid.

I have found that caramelized onions mimic the mouth feel and interest of cheese in some recipes. I realize it’s a long time since you made this request. Are you still looking for meals for your brother’s family now? My family has a quite a long list of restrictions too, and I might have ideas for you if you still want them.

Go wild with the herbs, lots of fabulous thyme and rosemary. They add interest to many dishes, especially par boiled potatoes finished in the oven.

Kale salad with pumpkinseeds and dried cranberries, tossed with a light vinagrette and some cooked grains....short grain brown rice or barley would work (I had it with farro, but since that's a wheat grain, they may not care for it).
Grilled or baked portobello mushrooms with vegan cheese.
Whole baked sweet potatoes stuffed with sautéed mushrooms and herbs (like a stuffed russet potato).
I have a recipe for zucchini stuffed with brown rice and lentils with middle eastern flavors...just skip the cheese topping. The filling could be stuffed into another squash, eggplant, bell peppers, or even a casserole. I've made it ahead, both raw and cooked, and even frozen it successfully.
Final suggestion is to tell them it's a potluck, and that your family will love whatever they bring...

I made this curry the other day and loved it (https://food52.com/recipes/24464-kabocha-squash-and-tofu-curry). You could definitely omit the soy sauce and use a can of drained chickpeas (or more vegetables) instead of the tofu.

Also, a big grain salad like this one (https://food52.com/recipes/39172-green-kitchen-stories-winter-millet-salad) might be a good option. Something with brown rice or quinoa or millet and then a bunch of roasted fall root vegetables. Super filling and seasonal.

Good luck!

You're to be commended. When you have that many requirements, especially self inflicted, you really should volunteer to provide your own food.

I'd suggest a roasted cauliflower (or squash, or aubergine), in a tomato based sauce. They're dishes that can be prepared well in advance and take reheating well.

Laurie Colwin suggested steamed vegetables with green sauce for these sorts of guests. IIRC correctly, her green sauce recipe was pureed watercress, scallions, lemon juice and olive oil with a bit of mustard. Could replace the lemon juice with vinegar.

What about a fritatta? Admittedly, it's not vegan because, well, eggs. But it is meat-free. You can load it up with whatever vegetables and herbs are desired. Bonus, it's not a particularly labor intensive or stressful prep for you.

I know it is more of a "summer" dish, but ratatouille would be wonderful and a nice change from squash. And all the ingredients are available year round. Serve with with quinoa.

You didn't say vegetarian. What about a baked fish?

how about these brussels sprouts with braised chestnuts? the recipe calls for butter and chicken stock, but you could substitute olive oil and vegetable stock. https://food52.com/recipes/38991-julia-child-s-brussels-sprouts-with-braised-chestnuts

Elisabeth this gussied-up version of butternut squash could work, minus the heavy cream: https://food52.com/recipes/9965-butternut-squash-puree. Could add some herbs or spices too!

What about this stuffing, leaving out the cheese, stuffed in a squash to be a little more seasonally appropriate? https://food52.com/recipes/36112-quinoa-stuffed-bell-peppers-with-basil-sauce