You need to immediately and privately consult with an attorney who practices in the area of civil litigation. Issues that may be litigated include the liability of a partner of a general partnership (https://en.wikipedia.org/wiki/General_partnership) and the doctrine of promissory estoppel (http://en.wikipedia.org/wiki/Estoppel#Promissory_estoppel).
You should see an attorney before you do anything else. Do not speak or write about this situation; only share what you know with your attorney. What you say to others can be used against you in court.
No attorney-client relationship is established via AVVO.com. The material posted by Kyle J. Bristow, Esq., is for educational purposes for prospective clients only and people should not make legal decisions based on it. You are advised not to take, or refrain from taking, any action based on what Mr. Bristow has stated on this website.
Obviously there is more to the story than you can type here. You should talk to an attorney in your area who is familiar with the laws in OH. You may have a contract claim, but if your part of the performance (your end of the bargain) was to marry this person and you failed to perform, then you may not want to go down that road. Contact an attorney who practices civil / family / contracts.
Providing this general response does not create an attorney client relationship.