Why do we think anyone knows? Obi-Wan can probably sense it and maybe Yoda, but they're supposedly living out a very exiled existence out of contact from anyone else. The Emperor used droids to build the Vader armor, so how would anyone make the link back to Anakin?
Tarkin - maybe since they work so closely at times and he's close to the Emperor. But I'd also bet he's not smart enough to ask or reveal it to anyone else.
Ahsoka - maybe if she comes in contact with Vader, but it's not like the Jedi can just mind read everyone in the galaxy. Vader can't really get a feel for Luke in the movies unless he's close by.
R2-D2 & C3PO - no evidence that either has a clue who Vader is. They're clearly afraid of Vader, but I don't see any reason why they would know he was Anakin at this point.
Bail Organa - he knows about Leia and the Jedi of old, so he's got an inside track. But what link does he have to knowing Vader is Anakin? Unless Obi/Yoda have shared with him, but when they split with the twins, I'm not sure even they know Vader is alive. I took that Obi left him for dead in ROTS.
Owen & Beru - I'd be shocked if they knew. They clearly knew Anakin had a dark side and very likely knew about the Tusken camp slaughter. I think that's why Owen doesn't want Luke to become like his father - not because he knows the Vader connection.
I'm more shocked that people didn't recognize Luke from his last name. Anakin Skywalker was probably all over the holo news during the clone wars. With only a generation going by, you'd think Luke Skywalker's name would have gotten around as having some potential connection. Maybe he was too isolated and young to register, but you'd think Imperial intelligence would be on the lookout for anyone potentially related to Jedi heritage (Kenobis, Windus, etc.).