Can I deposit a check payable to my husband's parents even if one is deceased?

My husband and I had some credit issues years ago, so his parents offered to put the mortgage in their name. They put out no monies for the home, we did that, they just offered their credit which we've kept in tact. We pay everything, mortgage, taxes etc. They never lived in the home. His mother ped away in August, now we just received our annual escrow refund check, payable to his parents in the form of "and" not "or." Years past, she always told me to sign it for them and deposit, and of course we never had a problem. Is there a way for us to deposit this check without her signature?