Reporting the passport stolen could be a huge hassle. First of all, it is a federal crime to report it stolen. Once you've reported it stolen, it cannot be used again no matter the circumstances. A new passport must be ordered, at a cost (in the USA) of $145. The brother would be charged with anything from attempted fraud to terrorism with a lot of other posisble charges in between. Sounds like a whole lot of bother for the brothers actions, which, BTW, were despicable. Just take him out in the country, beat the sh!t out of him, and dump him!

It’s not like the cat has anything to do with it. Only the brother is a douche

Oh, dear! You made the rookie mistake of taking me seriously. Airlines don't let cats fly unaccompanied. Also, no airlines publish fares to Hell. Except Spirit.

Replacing a passport usually takes a few weeks. And I assume they had their hotel booked as well, and I don't think they'd also be willing to change to booking last notice to a few weeks later.

The OP didn’t have their passport. Can’t get on a plane without it. I assume the brother didn’t give it back until OP was home.

You can get on a plane without a passport, this has happened before, but customs at the other end will catch it and send you back on the next plane back to your country if you can't produce it.

I am saying how could he not catch the next flight because typically if you kiss your flight airlines most of the time are nice and put you in the next one. OP stated “his brother handed the passport back.”

They said "shortly after," which could mean a few hours to a few weeks, the meaning is subjective. The brother might have waited until it was too late and then gave it back. Which makes him a major douchebag.