First thing I would say is get him gelded. If you don't you will be working against young attitude and hormones. Not a good mix unless you have experience working with colts/stallions.
In the meantime you need to earn his respect and establish yourself as the dominant leader. Its hard to explain this in one post although I can elaborate if you need.
If you have a older, exceptionally quiet, loving gelding I would put him with the gelding. A nice gelding can be the best trainer a youngen can have ;)