What grounds that a man can file annulment case because his partner is married again with other man?

A day after civil wedding, My cousin didn't see already his wife because the girl work abroad until now they haven't been together and he discover that the girl is married again after 6 years from the date of their marriage.

In my cousin's wedding, only his relatives know but for the girl, she don't have any guardian or parents that signed in their marriage license.

When my cousin knows that the girl is married again, he want to file an annulment case for his own and don't want to confront the girl because he don't want the girl to have problem in her new family.

What grounds of annulment that my cousin can apply without bothering the girl that married already with other man?

The only ground that I can think of is Psychological Incapacity, unless, they were married without marriage license or parental consent, (if the age of the woman during their marriage was between 18-21 years old)