2)Furthermore, a girl can call someone "kuya" as to cockblock him, emphasizing that the guy is only a brother to her, nothing more.
2) When the girl Jon was talking to started calling him Kuya, he knew the she didn't want to be involved with him.
You call them Kuya because either:
1. They are really older than you.
2. You want make sure they know that you don't want to date them.
3. You're just flat out mean!!!
Haha, you guys are the OFFICIAL kuyas.