1. It is not "valid ground" for divorce.
2. Hiding it from would be may become ground for annulment.
3. Ask him to search for a woman who sympathize his disorder and is ready to give in. Also there are many women who have OCD it just need the right eye for spotting one J In LCI family law forum also your friend can spot one or two.
4. Even if without disclosing he suppose marries then given to understand today's metro women, she will definitely use gender biased laws and seek not only maintenance but alimony and thus it will ruin his mid life.

Encourage him for multi-sessions of cognative behavioral therapy (CBT) it greatly helps for keeping a marriage stable.

Dear Sir,

    His parents are old and he is their only son. Will they also be implicated for hiding the truth? In case of annulment also, will alimony/maintenance be applicable? What are the gender-based laws by which they can claim alimony? Do you mean that if a girl were in such situation, she may not have same problem like gender-based laws?

Thanks