Is it permissible to strive to marry off one's brother to a girl with whom he has been in contact through social media and their relationship has developed?

It is advisable to consider the brother's seriousness and determination to marry the girl. If he is serious, then it is recommended to help him, seeking reward from Allah, as the Prophet, peace and blessings be upon him, said: "Allah helps the servant as long as the servant helps his brother." If the marriage takes place and is successful, then praise be to Allah. If it does not take place, then the brother must sever his relationship with the non-mahram girl, as emotional relationships between the sexes are not permissible. It should be noted that marriages based on acquaintance through social media often fail, so it is advisable to verify the other party through trustworthy individuals. It is also recommended to perform Istikhara (prayer for guidance), as it is one of the greatest factors for success.