It's hard to judge from the outside, but it seems to me as if too much attention is being paid to what the twins want to wear. It's good, IMO, to give them choices as others have described, w/in reason. But it should be understood that certain items are a necessity, such as wearing a coat in the cold weather or wearing pjs (clean, of course) to bed.
Putting the dirty clothes in the laundry when they take their bath/shower is a good idea. Another is, of course, giving them a choice of fave pjs - possibly ones w/ fave characters on them (Disney princesses or whoever). Failing that, it may be best to tell them they have a choice between getting in their pjs or sleeping in their underwear. And fine, if they pick the latter, but they still don't get to wear the dirty clothes.
Of course, unless you watch them at night, that part is all up to the parents. And really, so is establishing the idea that coars are a necessity. But one thing you can do, I'm sure, if you try, is not show that it upsets you if they don't wear their coats. (I know it's hard, but I'm certain you can manage it.) If they complain about the cold, offer them their coats, once again, but if they still refuse, let it be. If they whine, let them know that they can wear the coats or "freeze" - their call. If they want a choice, that's it. Chances are, they'll realize, after a while, that they need the coats.