Did Owen and Beru Know Anakin Was Vader?

This is more of an in-universe thing. Owen and Beru definitely know that Luke is Anakin Skywalker's son, but it's not common knowledge in the Galaxy that Darth Vader is Anakin Skywalker.

Did Uncle Owen know Vader is Anakin?

Though it sounds like he thinks Anakin is dead, he could also be viewing it as Obi-Wan does, where he believes Anakin died when Darth Vader was created. There's a hint that Owen knows Anakin was Darth Vader by the time of A New Hope.

How are Owen and Beru related to Anakin?

Cliegg's son, Owen, married a girl named Beru Whitesun. When Anakin Skywalker, the son of Shmi, became Darth Vader, his son, Luke Skywalker, was cared for by Owen and his wife, Beru Whitesun, whom he called "Uncle Owen" and "Aunt Beru." They were killed by Imperial stormtroopers in 0 BBY.