How can one be sure that a brother is afflicted by sorcery, especially with the change in his character and the loss of his jealousy towards his wife, and how can he be treated with Ruqyah from afar while he is in another country?

There is no definitive way to ascertain whether a person is afflicted by magic, and ruqyah is permissible whether or not the person is afflicted. As for ruqyah from a distance, it is not without benefit, especially if accompanied by a prayer in the absence of the person. However, blowing is essential in ruqyah, and this can only be achieved through direct application. Furthermore, there is no harm in reciting some Qur’an with the intention of interceding with Allah Almighty for your brother’s healing, as this falls under the category of permissible tawassul, which is tawassul through righteous deeds. If you are unable to perform ruqyah directly on your brother, then supplicate for him and seek intercession through the recitation of the Qur’an; for supplication benefits both those near and far.