In this scene, Uncle Owen says Obi-Wan Kenobi died about the same time as Luke's father. And Owen tells Luke to stop asking about his father.

Did Owen know Anakin was Luke's father? I think he would know since otherwise, why else would Kenobi ask him to adopt baby Luke? I can't imagine Kenobi getting away with some excuse like this. "Hey, here's some random baby. Why don't you look after him? Oh, his parents? Nevermind them. They were killed by Jawas on the south ridge." "But Mr. Kenobi, why are you giving us this baby?" "Oh, you look like nice people."

Kenobi surely had to say something about Luke's father. We know he chose Owen and Beru because of the family connection to Anakin. And if he said Luke's father was that local boy who became the galaxy-wide famous Jedi hero of the Clone Wars, then wouldn't everyone from Mos Eisley to Anchorhead know "Hey, there goes Luke. That's the son of Anakin, the Jedi hero. Remember when Anakin was a little slave boy and how he finally won the pod race?"

So what did Uncle Owen and Aunt Beru know of Luke's real father?

The video snippet indicates he seems to know, but didn't know the whole truth (maybe Kenobi lied to him or at least clearly didn't say everything about Anakin's true fate). But Kenobi telling Owen and Beru seems like a major risk given how famous Anakin was and even bringing the baby to them is a major risk.

Owen outright lies to Luke by saying Obi-Wan Kenobi died years ago - about the same time as Luke's father. He knew Obi-Wan Kenobi was that crazy old wizard, Old Ben Kenobi. He should have known that if Luke learned that Obi-Wan Kenobi was still alive, then Luke would not trust him.