I get married next Spring, and gave notice this week.
Part of the questions was about my parents. I told the registrar that my dad was deceased, and she said we'd put his details anyway, because people might want to use it for ancestry tracking etc. She was lovely and talked about how she'd lost her own father a few years ago, and what had helped her. She was excited to say that my mothers details may well be able to be included by the time I get married.
What I didn't tell her, because I didn't think it was relevant, is that my parents were very abusive before they died. I don't want either of them on my certificate. I don't really feel they deserve to be there, and I don't want any of their family to track me down. I just strongly don't want them on it.
The wedding has bought all this to the fore for me a bit - there's so much that involves your parents - and I don't know if IABU to not want them there... I have no idea if it's possible for them not to be.