I would err on the side of skeptical. There is, of course, every chance that they are legitimate, but the number of fake Dali’s out there is pretty enormous. I would suggest getting as much background on where they originally came from to start. Where did your relative get them from? How long ago? From whom? I have not looked into it recently, but there are most likely books out there too designed to help with authenticity of Dali’s prints. If you were willing to do a bit more digging, you might see what, if any, museums have versions of the same prints and what they can tell you about the series. They may know if there are a lot of fakes out there, how many originals were made, etc. Most museums have a research department you can contact for such inquiries.