Rey is Luke’s Clone
“Star Wars” loses it’s mind for clones. Having Rey be a clone of Luke isn’t as much of stretch as possible. Most theories suppose that the First Order is behind said cloning while trying to create a Force User to take down Luke. There are even a couple different ways they could have acquired his DNA.
The obvious way would be from Luke’s severed hand. We already know his lightsaber was recovered — Maz Kanata was keeping it in her cantina — so if that was found it stands to reason Luke’s gross hand could have been found somewhere too. The other way would be from Darth Vader’s helmet. The First Order already has the helmet — how they got it is a mystery — and Luke took the helmet off Vader as he was dying at the end of “Return of the Jedi.”