Yeah sure it’s okay, just make sure you ask your brother if it’s okay with him first - or get the guy to ask your brother if it’s okay. :)
Why don’t you message him online to start? Or ask your brother about him.
Whenever my boyfriend gets all stressed out I take him out somewhere to have fun. Like the aquarium, or to a movie or dinner, etc, and we just have a really good time and forget about his stressors. It’s a big help and it’s good for him to clear his mind. You should always be open to talk and try to find solutions if needed, and ask him if there’s anything you can do to help.
It sounds like he thinks of you as (don’t hate me) a puck bunny. Usually when guys only talk to you later at night thats a big indicator, have you gone along with the conversation? I’m not sure what to tell you on that one, I myself would steer away from him if he was doing that to me. But it’s up to you, I would just tell him how you feel and try to have normal conversations with him to get to know each other better and do not participate in any late night talk.