I have an American Eagle, Aeropastel and Gap household! ... ha ha, just kidding. I do, but it's all stuff I got from Goodwill. All under 10 dollars each. I'm a clearance rack at Target kind of gal too or ebay on occasion.
For those concerned about sizes and the plethora of ones you "are"... Don't. It's all a psychological thing. You're not a freak, it literally is a marketing game aimed to psychologically make you feel better. It started a few years ago, I worked at Bath and Body Works and we used to get 50% off of Gap clothing being we were the same company.
I went in and always got the same size. A year and a half later, they were celebrating one of their anniversaries, I went in, used my employee discount to add to theirs and bought a whole load of my size. Went home, tried them on and nothing fit. I took some of the jeans that were same size, same brand, same everything and looked at them side by side.
I went in, returned everything and got the right size and then talked with the manager whom I was close to as I babysat her kids. She smiled and nodded and explained.
"If you went to say (insert brand name store here) and tried on pants at a size 8, then wandered over to our store, found some pants you liked and tried on an 8 and then found it didn't fit you and tried on a 6 and it did, where would you buy from?"
She knew I studied psychology and would get it so I just shook my head. But she was right. Psychologically women need to feel like they're gorgeous because we never quite think we're perfect. And if we can say we fit into a 6 when in others we fit into an 8, we're going to keep going back and purchasing stuff at the store we're "smaller' in. We need that lift. It makes us feel good about ourselves and when we feel good about ourselves, we are more likely to part with our money to keep that good feeling going.
There is, however, the sizing mandatory issue that tries to keep everything in the realm of distinction. I forget what the law is called, but it's supposed to keep some sort of regulation so there's not to disparaging of a discrepancy between the sizes. But, at least now you know why you're across so many sizes depending on brand!