I see your "Nicky likes to steal other people's clothes" headcanon and raise you "The Foxes like to steal Nicky's clothes."
-Erik steals at least one sweatshirt every time he sees Nicky because he wants to be able to wear clothes that smell like his boyfriend.
-Andrew likes to pretend that he hates Nicky's fashion sense, but secretly borrows clothes that he wants to try out before buying his own size.
-Aaron stealing sweaters from Nicky during the winter because they are super cozy and him stealing even more clothes when the cousins part ways because he wants to always have something that smells like home (i.e. Nicky)
-Neil stealing hoodies on days he's feeling self-conscious about his scars, so he likes to wear Nicky's hoodies because he just absolutely swims in them. (Neil sometimes steals Matt's hoodies, but 9 times out of 10 its actually one of Nicky's that Matt stole lol)
-Matt likes to steal Nicky's dress clothing. When Matt takes Dan to fancy restaurants, he finds out what she's planning on wearing and then he checks his closet to see if he has something that matches. If he doesn't, then he checks Nicky's closet. Nicky always has the perfect outfit!
-Kevin pretends be doesn't steal clothes from Nicky, but he definitely does. Kevin can't help it that Nicky's sweatpants are sooooo much more comfortable than his own. If caught, Kevin gives the excuse that they share a room and that Nicky's sweats must have "accidentally" made their way into Kevin's laundry pile.
-Renee doesn't steal so much as borrow Nicky's skirts. She thought she had a vast collection until she met Nicky. She always asks before she takes them out of his closet, and she's great about giving them back in a timely manner.
-Allison steals Nicky's jackets like it's her job. Yes, she can buy whatever she wants whenever she wants to, but she LOVES Nicky's sense of fashion (even if she won't admit it) and so she loves to take his leather jacket and wear it over her favorite crop tops, or take his neon pink windbreaker and wear it with matching neon pink shorts. She steals Nicky jackets so frequently that Nicky honestly doesn't even know which ones are his anymore and which ones are actually Allison's.