So basically I and my brother go to school together and we share funds. I pay for our transportation and then at the end of the day we calculate everything then he pays me his half. But I've noticed that when it comes to him paying his half he'd playfully threaten me that he wouldn't pay. It gets me angry and I usually tell him I don't like it but he keeps repeating it. He then says I'm getting angry over small money but that's not the case. It's annoying how he keeps playing with my feelings like it's a joke. What do I do? And is what he's doing right?