Haha, totally understood!

Bear in mind (again, this is on my airline. YMMV) that because you aren't married (I would sure hope! ) the IRS sees this as a taxable benefit. Therefore, every time an airplane takes off with you on it, your brother will be subject to "imputed income" - which is kind of a "ghost" income that you don't actually see on your paycheck, but you get taxed as if you had. That is, they add the imputed income to the wages made in that paycheck, calculate the taxes owed, and subtract that income again. Obviously, higher income = higher taxes. I think that makes sense. If not, let me know what you're confused by and I'll explain it better. Anyway, different routes would have different amounts of imputed income, but it's certainly still cheaper than a normal ticket! Just something that can add up. Also, being a sibling, I can pretty much guarantee that you will not be eligible for ZED fares (discounts on other carriers). Maaaaybe on a select few carriers if your brother flies with you, but I'm not sure if oneworld does that (United has that for about 5 other airlines)