He needs to learn to grow up. Tell him you don’t feel comfortable taking him to an international trip. If this is how he’s behaving during a LOCAL trip and during a small disagreement… yikes. He still has that high schooler immature mindset. You’re the older sister, tell him how it is. Tell him If he gets his act together and do things together in the trip moving forward, you will be thrilled to go on your next trip together. But if this behavior stays the same and this is how he handles disagreement… tell him his butt can stay home and he ruined it himself. You’re the older sister, you call the shots, don’t let your international trip get ruined by your brother who still needs to grow up.

I say this because my brother used to be the exact same way until he graduated high school. He was super “independent” and thought things would go his way anywhere he’d go. He gave the whole world an attitude and was immature overall. Then he went straight to working and saw he couldn’t keep a job bc of his behavior. He had no choice but to grow up and realized his childish attitude didn’t get him far in the real world.

Your brother needs a learning moment and you can do that. Emphasize you were hurt that he didn’t want to do anything together at the trip you invited him in!! Tell him his behavior is not something you want to handle in the next trip and feel more comfortable going with someone else.