Life insurance policy?

My fiance passed away in October 2009. I was not a beneficiary to the life insurance policy his mother was. While he was alive he provided a house for my two children and I. We had two loans together and would split some of the other bills together. Now they have recently gotten mad at me for the way I have moved on they are not willing to give me any of the life insurance money to help with the car loan we joinlty had. I was originally not asking for any money but now that I have become accustumed to a combined income of about 130,000.00 a year to one income of a little over 25,000.00 has left us without out a home and now a car payment of about $600.00/month that was purchased 2 years ago. Is there any possible way they could be required to pay some of the debt that was acquired jointly in our names? Is there anyway in the state of Oklahoma to proove common law marriage for us?