Marriage between a Mahdavi man and a Sunni woman
24-8-2011 | IslamWeb
Question:
Is marraige between mehdawi muslim boy and sunni muslim girl valid or valid? Some people say its valid because both girl and boy believe in ALLAH SWT as one and only god..but theres who say such marriage is invalid.plz give ur opinion
Answer:
All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.
It is well-known that it is unlawful for a Muslim woman to marry a disbeliever. Mahdavia was founded by Muhammad ibn Yoosuf Al-Jaunpuri who was born towards the end of the 9th century (Hijri) in the town of Jaunpur in India, and claimed himself to be Al-Mahdi. The followers of this sect believe that Muhammad ibn Yoosuf is the promised Mahdi and that he is better than Abu Bakr, ‘Umar, ‘Uthmaan and ‘Ali 
and even better than Aadam (Adam), Nooh (Noah), Ibraaheem (Abraham), Moosa (Moses) and ‘Eesa (Jesus), may Allaah Exalt their mention, and equal in rank to our Prophet Muhammad, sallallaahu ‘alayhi wa sallam, though following him in doctrine; and that only he and Muhammad, sallallaahu ‘alayhi wa sallam, are perfect Muslims, whereas Islam of all the other Prophets is incomplete. They also believe that he has some divine attributes after he attained the rank of apostleship and Prophethood.
No doubt, those who hold such beliefs become disbelievers and go out the fold of Islam, and it is impermissible to give them Muslim women in marriage or to marry their women.
For further information, please refer to Fataawa 81406 and 156501.
Allaah Knows best.