Victor Fong, Licensed Insolvency Trustee in Toronto, Canada replies:
Caveat: I am a bankruptcy trustee in Canada, so I am unfamiliar with the U.S. Bankruptcy Code (I assume you reside in the U.S.). So I am going to provide an answer if your situation was in Canada.
The answer is “no”, you can just file bankruptcy on your own. However, to the extent that your debts are joint with your fiancé, the creditors which are owed these joint debts will be able to go after him to recover what they are owed.