NC with family member but family still passing on information

[SushiSuave]

Not sure how to deal with this situation so looking for advice. I went NC with a parent 3 years ago due to their horrendous behaviour beginning to affect my son, and me drawing the line at that. Since going NC I have been so so much happier, my anxiety has reduced dramatically and I just feel free. However, my sibling is still in contact with this parent and discussing me and my family on a regular basis with them. I know this is a very difficult situation for my sister, and the narcissistic parent still claims to love me and miss me every time they speak to my sister and guilt trip her into trying to get me to make contact again. My sister completely understands my view point on this and does not try and persuade me to do anything which I really appreciate. However, I have found out they they still regularly talk about me and my family and what we have been doing. This irritates me greatly as I don't believe this parent has any right to know anything about what me and my family are doing or our "news". We will soon be moving to a new house that NC parent will not have an address for. However, I am sure they will ask my sister where we are living. I don't want parent to know. How do I deal with this? Telling my sister not to pass this information on will put her in a difficult position with NC parent, and I know parent will continually ask her until she gives in. I also don't want to fall out with my sister. However, part of me feels like saying to her that I can't give her my new address unless she can promise not to tell parent. Is this unreasonable of me? Is there a better way of going about this that won't lead to any animosity between me and sister, but will also keep my privacy from parent? I can not stress how lovely my sister is and I know she is navigating me being NC with parent in the best way she can but am getting annoyed with parent still being so up to date on my life without my permission.

I'll be honest, it depends a lot on why you chose to be nc. My ex mil was quite frankly horrible to exh but he never cut her off, she's his mother, we just didn't have much to do with her (saw her at other family houses by accident etc but he never rang her etc. she still sends me a Christmas card). This approach means you don't pander to the parent but nor do you put your sister in this position. There's reasons why people are the way they are and every complete family breakdown are not one way - think about it

Unfortunately this parent is all or nothing. If I'm in contact it's 10-15 phone calls a day, abusive voicemails when I don't answer, constant expectations of me, rudeness, public shaming of me and how I parent (ironically), open sexism, racism, homophobia and constant criticism of everything I do. At the age of 29 and when this behaviour started to become directed towards my then 3 year old son I decided enough was enough, and "nothing" was the way it had to be to protect my self and my son. I have 0 regrets and am 100% sure that going no contact is the best thing I've ever done.