Did Owen and Beru know?

They accepted wee!Luke and raised him well, but did they KNOW what Anakin had turned into, really? If they did, when did they find out? ( Because it's not like Obi-Wan would have told them... )

That knowledge might be why they died -- refusal to cooperate with the stormtroopers for fear for Luke could have made them intolerably obstructionistic to the troopers chasing C-3PO and R2D2.