Why is it that a kaafir who blindly follows his family deserves to go to Hell, but a Muslim who blindly follows his family deserves to be saved?

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.

First of all, you should know that Allah, Blessed and Exalted be He, is wise, and that He, Glory be to Him, for the perfection of His Wisdom, is not asked about what he does. Allah Says (what means): {He is not questioned about what He does, but they will be questioned.} [Quran 21:23]

You should also know that Allah will not punish anyone except after establishing the evidence on him and removing the misconception from him. He revealed the Divine Books and sent Messengers and did not leave any room for excuses. Allah has established clear-cut pieces of evidence, proofs and sings, that are clearer than the sun in the bright day-time about His Oneness and the truthfulness of His Messenger . Therefore, whoever kept a blind eye on all of this and just blindly imitates others and does not follow the truth whose evidence is made very clear, then he deserves to be punished by his action and his offense, and your Lord is not ever unjust to [His] Servants.

As for whoever Allah has guided to Islam by being born in a Muslim environment, then that is the bounty of Allah which He gives to whom He wills, and Allah is the possessor of great bounty.

Being born in a non-Muslim environment does not necessarily lead a person to disbelief. Verily, there are many people whom Allah has guided to Islam when they knew the truth and searched for it; Allah guides whomever He wills to the Straight Path.

For more benefit on the merits of Islam, please refer to Fataawa 85456 and 102075.

For more benefit that Islam is from Allah, please refer to Fataawa 88176 and 85234.

For more benefit on the comprehensiveness of the religion of Islam, please refer to Fataawa 81929, 86091 and 82057.

For more benefit that Islam is the religion of all the Prophets, please refer to Fataawa 81979, 88906 and 88051.

For more benefit that everything in the universe testifies that Islam is the true religion, please refer to Fatwa 111063.

Allah knows best.