Board Thread:General Discussion/@comment-1491767-20170410021412/@comment-26397825-20170410025918

We don't have any actual confirmation on Sun's age, but given that when Miles and Kerry answered the question of 'When are RWBY going to meet an older team?' and the answer was that they had met CFVY, not SSSN or anyone else, I believe he is supposed to be the same age as Blake.

As for his past...

He moved from Vacuo to Mistral to attend Haven, Mistral's Huntsmen Academy. I'm not sure that there would be anything special about it, since it's not like students are forced to attend Academies in the same Kingdom as they are. Look at Nora, Ren, Pyrrha and Weiss. Weiss has a reason in that she wanted to get out from under her father's thumb, but the other three don't really appear to have one. Sometimes people just want to go somewhere else for their college experience.