Greeting?

Aside from my older brother, my whole family only makes visitations to my grandparents' place when there's an occasion like Christmas, fiesta, or any other event which only happens once a year. I didn't know any other person in that place other than our close relatives mainly because of the fact that I don't go there often. This is the reason why I had to stick to my brother for the whole Christmas break.
Kuya was so popular on that place, it was like he has friends all over the place. One time when we were on our way to the Barangay Christmas party, we met a guy on a motorcycle. It was Junrey, one of my brothers friends. Kuya greeted him by just raising his eyebrows and all of a sudden they were talking with each other. Their long conversation made us twenty minutes late for the party. While we were enjoying the party we met two girls - Marie and Ronna. Kuya smiled at them said hello but unlike what happened with Junrey, no conversation happened.
Why did a simple raising of eyebrows started a long conversation, while the smile and a hi wasn't able to do the same effect?

After the party, I asked my brother who were those two girls. He told me that Ronna was her girlfriend and they just broke up for they found out that we are close relatives. It was only then when everything began to become clear. The problem was not on the way he greeted but on the relationship of the sender of the message to the receiver. When kuya greeted Junrey they didn't have any problems with each other hence, he was comfortable talking to Junrey. On the other hand, since my brother was so conscious on what might Ronna or the other people react if they talk, his level of uncertainty boosted. When his level of uncertainty of what might happened increased, the chance of him interacting with Ronna deceased provoking him to hide his inner layer.