Is Monster 日本动漫 suitable for 10 或者 12 年 old boys?

NO NO NO! This is FAR from material for their ages. This is an adults anime

Windwaker is right, I wouldn't let them watch it YET but if they're mature and able to handle adult concepts in a few years, I would recommend it then. There's no nudity, though there's quite some violence in the blood department. When they're 13-15 if they're mature, I would say go for it ^^