My ex husband and I rarely communicate. As infrequently as possible since we divorced almost 17 years ago. We cannot get along and my ex lashes out at me over the guilt he has for being in and out of jail and rehab my son's entire life. My ex has admitted it's his guilt and apologizes for how he acts but he can't help himself and is like a broken record. I have NEVER asked my child to communicate for me or handle anything sensitive. I think your parents are asking too much from you and you need to tell them so at some point or another. (((Hugs))))

I'm sorry about your sister.