As I read your post I felt like this is some kind of possession. Even if it does have an organic factor, those were placed in us by satan at the fall and give demons hand holds on our soul. But this sounds seriously spiritual in nature. Pray, those around you should fast and pray. Speak Jesus' Name over his name to bring him under Jesus covering. Names have to do with spiritual authority, you need to put his name under Jesus' authority. Then whatever the name of the demons are, they've got a pretty substantial roadblock to getting at him.
A lot of this will require confession and repentance to shed. Identifying particular sins of his past and getting him to confess them is very helpful. When we submit in sin to a spiritual authority, we are submitted to that spiritual authority until we rebuke it by confession and repentance. You can pray for him in this way too, but it works best when he does it.
This of course may be hard if he won't talk. But there are spirits that will strike you dumb. Don't be afraid to bind and silence them, and if they give you any grief tell them to go talk to your Supervisor. Pray his tongue be loosed that he may confess. If you pray in tongues it may help. There is power in the spoken word and that is part of the power of prayer. But you can only speak to the things you know of. There's probably a lot going on that you don't know about, so how can you speak in prayer to them? The Holy Spirit knows, if you allow the Spirit to pray thru you, you can speak to those mysteries you know nothing about.
And I throw that last in with no pressure that you do so. I don't know what you believe about that, I'm just saying it's an option to consider.
And of course don't put off earthly doctors. God has given them ways to help subdue the flesh. And your cousin needs all the help he can get it sounds like.
Father God, I come before you happy as always that I may, yet beholding in my usual giddiness by the seriousness of this approach. You know this person better than I do, You know this situation better than I do, You have an answer for it before I even come before You! Father flow your Holy Spirit into the situation and these people, gift them with knowledge and wisdom and words to address the mysteries You only know surrounding all this. Give them boldness to bind and silence spirits and loose tongues. Father may angels attend these, to minister and bear them up; and even more by Your power to occupy and do battle with the enemy. Lord as Gali faces these demons to command them bound, I pray with her claiming Your word of where two or more are gathered to seal them. Bring her people to lead her and teach her how to lead and teach her cousin... and her family. Embolden her, that in Your Name she may be bolder than the opposition. For Your authority , thru us, is greater than the oppositions. So why shouldn't we be bold? And Lord bless those doctors and others who prescribe care, may Your Spirit gift them as need be also. Father, it is only by the Blood of Your Son that we may approach You, it is only by the Blood of Your son that this flesh will be rid of those who take him away. I pray the Blood of Jesus over Gali, we pray the Blood of Jesus over her cousin, and we rejoice and praise and give You thanks that we may. And that You honor us so. Lord honor Gali's faith, as she has come before us to confess her need, may it be answered so a hundred fold.
In Jesus' awesome Name,
Amen!
