Here is the original item:
Despite her parents' disapproval,
(A) Tran
continues to date Charlie.
(B) A nice young
man (C)
whose only fault is not being born Vietnamese.
You wanted to do this:
Despite her parents' disapproval, Tran
continues to date Charlie. A nice young man. Whose
only fault is not being born Vietnamese.
Adding a period after man creates a fragment. Whose only fault is not being born Vietnamese is a subordinate clause, which cannot stand alone as a sentence. Reconsider your options.
You might want to review the rules.