How can one confirm that my brother has been afflicted by jinn or sorcery after his return from a long journey and the strange change in his behavior, and what is the method of his treatment in this case?

The difference between jinn possession (mass) and sorcery (sihr) can be identified by several signs:

As for jinn possession, its signs include: aversion to hearing the adhan (definition) (call to prayer) and the Quran, fainting or convulsions during recitation (ruqyah (definition)), frequent terrifying dreams, isolation and strange behaviors, the jinn possibly speaking during recitation, and staggering, as in the Almighty's saying: "Those who consume interest will not stand [on the Day of Resurrection] except as one stands who is being beaten by Satan into insanity."

As for sorcery, its signs include: the bewitched person's hatred for his wife, a difference in his state inside and outside the home, inability to have intercourse with his wife, repeated miscarriages for a pregnant woman, sudden changes in behavior, lack of appetite for food, imagining doing something without actually doing it, and blind obedience to a specific person.

It must be noted that these symptoms may also be due to other organic or psychological causes.

Treatment involves reliance upon Allah, and legitimate incantations and invocations such as al-Mu'awwidhatayn (the two surahs of refuge) and al-Fatiha. In the treatment of sorcery, seven green Sidr leaves can be used with the recitation of specific Quranic verses over them, followed by bathing and drinking the water from it, extracting and destroying the sorcery, and using permissible remedies such as eating seven dates on an empty stomach, cupping (hijama), and supplication.