In Episode III, when Anakin buries his mum, Shmi, on the Lars' farm. There are two other burials there, too. Who is buried in the two other graves? And, were these burials shown on Uncle Owen's farm in ANH or no?
Cliegg's first wife and a baby. I think from EU sources that Owen moved the graves in between ROTS and ANH but I'm not 100 percent sure on that, nor do I know the logistics of how moving graves on a primitive desert planet would work.
Jim Smith, in his biography of George Lucas (Virgin Books), oddly states that Shmi's grave is actually visible in ANH... I took a close look once, and never found anything. Highly doubtful anyway, as no added effect has ever been mentioned about this.
Luke probably backed the landspeeder over them. Naw, I think Obi-wan lifted them and dumped them somewhere. What struck me funny, even though there is a TON of rocks around there is nothing like a headstone maker nearby yet they have one with Shmi's name and date on it in like 2 hours.
They never showed that camera angle of the Lars farm in the OT, they're probably still there in Luke's time. Owen was really close to Shmi, no reason to hide her existence from Luke.