Is a Christian brother by fosterage considered a legitimate brother by fosterage?

Foster-brotherhood is not affected by religious differences. He is considered your foster-brother, and it is forbidden for you to marry his daughters, for the Prophet, peace and blessings be upon him, said: "What is forbidden by lineage is forbidden by fosterage."

You must strive to invite him to Islam, for the Prophet, peace and blessings be upon him, said: "That Allah guides through you one man is better for you than red camels."

It is permissible to show kindness to him if he is peaceful towards Muslims, for Allah, the Almighty, says: "Allah does not forbid you from those who do not fight you because of religion and do not expel you from your homes - from being righteous toward them and acting justly toward them. Indeed, Allah loves those who act justly."

However, it is not permissible to love him in the sense of loyalty or to take him as an ally, for Allah, the Almighty, says: "O you who have believed, do not take the Jews and the Christians as allies."