Question:
May I chat with my 12 year old male cousin? I am a 20+ years old woman.
Answer:
If it is just schmoozing, because you enjoy his company, then it is improper, the same way it is improper to talk to any other 12 year old boy. He is not a brother, and the same way a woman can't be in a yichud situation with him, can't have a physical contact with him, she can't just schmooze with him.
Best wishes