How do you know what the right path is for them? I think it would be best to let this person find their way back, if it truly is their right path. You can also talk to them about it, explain why you think it is their right path. Just do not force it on them, trying to force it on them can cause them to never come back to it at all. If you really do need a spell, you can try one to help the person think clearly, however this might not work if you are hell bent on them seeing it your way. Remember, your way may not be the correct way either, you never know. :)
I have to agree you think different from the other person. How do you know the way you think is right!
We are all human we think differently and agree and disagree on certain things.
Everyone has the choice to what they think is right and what is wrong
Try reaching out to your Spirit Guide and ask them to contact your friend's Guide to see what help, if any is needed, that you can give. Just because you do not like where they might be headed, doesn't mean that they are on the wrong path. To me the only time for direct intervention would be to stop self harm (death, spiritual damage).
Send prayers out of protection and guidance for your friend. Give them true love. Sometimes it hard to see other's "falling or straying" from the path, but look to your path first so you too don't get lost.
Use the power of cristals! A pink Quartz have the strong power to conect with our heart. Made a spell of your own imagination to calm down your brother (cast this spell into the cristal)and in this spell, dont forget to say that your brother must change RIGHT NOW.
Then, hide the crystal in your brothers pillow. When we sleep, most of our defense fell (thats the reason people who was cursed notice this first when have nightmares).
The spell will change your brothers mind. Be confident, the more you trust in your power to cast a spell, the more effective this spell will be.