He is not a muslim and he can not marry a muslim girl if he has such beliefs. You must expose him to them and treat him as a kafir.

my brother believe in Rasool Rashad Khakifa who came after our Prophet Muhammed(pbuh)& as per their Rasool they have deleted last 2 verses of Surah Taubah.Our father knows these things and with other family members they are purposely hiding this from the Bride & the Parents of the Bride & asking us to cooperate in this marriage.Pls advise how can we support this marriage.

Fiqh of Marriage | November 16, 2015 4:45 am
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Suppose a muslim man and an atheist girl decided to marry, and the atheist girl has agreed to convert to Christianity by getting baptised in a Church. That is, she is not willing to become a Muslim, but willing to become Baptised Christian before marriage day. Should the man marry her?
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My niece suffers from jinn poession. My family would want to keep it a secret from her prospective spouse. Is this the right thing as they want to go far to lie?