Should i tell my x's family why he's ill?

I found out that I am HIV +ve 2years ago. I contacted the disease from my baby's father whom I broke up with a year ago since things were not smooth anymore. After i had found out about my condition i started with my treatment 6months later. My x never took any treatment, for what reason, i have no idea. Now his family called me to tell me that my x was admitted to a hospital, i think they dont know what his problem is? Should i keep quiet coz it was his(my x's) responsibility to tell his parents about his condition and take treatment? Now they're putting me in a tight corner coz we're not together anymore but his parents want me to check on him. I feel so bad coz i know whats wrong with him. What should i do?