brother with undiagnosed ppd-need to get him to a doctor

For quite a number of years my brother has expressed concern that people talk behind his back and are not genuine with their comments. Over the past few months he has begun to ask family members if they were a part of an intervention of him. He has now opened up to my father telling him that he believes people are conspiring against him, tapping his phones and computer, breaking into his house and has been seeing messages written in text on his television. He has not opened up to me about this so I am hesitant to discuss it with him so that he does not see that now we are talking about him, if only to help him in his situation.

He has a long history with cannibus and I wonder if he were to stop it if he would have this situation go away, or at least lessen. I have discussed this with him but he feels as he is a musician that he wants to keep doing this.

I am trying to figure out a way to have him speak with a therapist of some kind but can't seem to find a way to get him there. I have discussed with him over the past few years that he may benefit from someone objective to talk to but he won't bite.

I have done alot of reading on the net about ppd and he has all of the symptoms.

If someone had some thoughts on this I would really appreciate it.