help joint mortgage no equity

Hi all I made a wrong business decision 5 years ago. I bought a property with family member as investment. We then fell out and I have had nothing to do with property for over 4 years. I believe he rents property out and property is in negative equity. I would like to get out of the mortgage but I am not sure if his salary is enough to get the mortgage on his own, although, the mortgage is paid for by rent. Is there anyway for me to get out of this Mortgage or will I have to wait till property is back in equity and se if he will sell.

Thanks.