Welcome to BB and thanks for reaching out.
It sounds like it's been really difficult for you to be estranged from your family and I can see why it's affecting you now. I think before you even consider talking to your daughter you first need to decide what it is you want and the kind of relationship that you can have with your family now. Are you able to see them at all? Can you update them via phone/email on things that are going on with your daughters life? Are they willing to meet you halfway? The way I see it only you and your family know these things and can come to a compromise on the amount of contact/connection you can have.
I think that talking to your daughter is important though, and trying to give her direct answers. Depending on how young she is, if she's told they are "in another world" this might only ask lots more questions. I would suggest telling her a short version and trying to be non-judgemental "They love you very much but they have their own lives over in (place) so we don't talk very much". You may even want to show her pictures/tell her stories so that she has an understanding of who they are.
It may even help to have a chat with a counsellor or the BeyondBlue hotline for some advice.
Hope this helps.