Yes, the answer would be a spoiler.
Read at your own discretion.
As it stands, MC potentially has 2 sisters. 1 is in a wheelchair, with a mental disability. So you're not fucking her. She's not confirmed conclusively to actually be his sister, as yet.
The other is not proven to be his sister yet, either. It's just been found out from the DNA test at the end of ep4, that the blonde whose father is in prison is MC's half sister. They both have the same father. But it feels like this could be something spun by the people pulling the strings behind the scenes, so may not actually be the case. We'll have to wait & see.
As for your vinyl analogy, you still had to listen to them in the record store, before buying them, to find out. So the answer of "play the game" is the same premise.