English _fellow_ has multiple meanings and it's impossible to give a catch-all term. For reference, here's what ALC says:
> 1. **** **** ****
> 2. **** ****
> 3. **** ****
> 4. **** ****
> 5. **** ****
> 6. ****
> 7. **** ****
> 8. ****
>
* * *
You can use when it's close to "colleague", () when the sameness of social status or generation is important, for this sense, and for this sense. If it refers to teammates of an in-company sport team, or should work. When in doubt, you can always say , or such. is awkward because it sounds like "fellows who are also members (of another group)" or "members of (a group called) _Nakama_ ".